Challenges in Defining a Reference Set of Differentially Expressed lncRNAs in Ulcerative Colitis by Meta-Analysis

The study aimed to identify common differentially expressed lncRNAs from manually curated ulcerative colitis (UC) gene expression omnibus (GEO) datasets. Nine UC transcriptomic datasets of clearly annotated human colonic biopsies were included in the study. The datasets were manually curated to select active UC samples and controls. R packages geneknitR, gprofiler, clusterProfiler were used for gene symbol annotation. The R EdgeR package was used to analyze differential expression. This resulted in a total of nineteen lncRNAs that were differentially expressed in at least three datasets of the nine GEO datasets. Several of the differentially expressed lncRNAs found in UC were associated with promoting colorectal cancer (CRC) through regulating gene expression, epithelial to mesenchymal transition (EMT), cell cycle progression, and by promoting tumor proliferation, invasion, and migration. The expression of several lncRNAs varied between disease states and tissue locations within the same disease state. The identified differentially expressed lncRNAs may function as general markers for active UC independent of biopsy location, age, gender, or treatment, thereby representing a comparative resource for future comparisons using available GEO UC datasets.

DNA methylation fine-tunes pro-and anti-inflammatory signalling pathways in inactive ulcerative colitis tissue biopsies

DNA methylation has been implied to play a role in the immune dysfunction associated with inflammatory bowel disease (IBD) and the disease development of ulcerative colitis (UC). Changes of the DNA methylation and correlated gene expression in patient samples with inactive UC might reveal possible regulatory features important for further treatment options for UC. Targeted bisulfite sequencing and whole transcriptome sequencing were performed on mucosal biopsies from patients with active UC (UC, n = 14), inactive UC (RM, n = 20), and non-IBD patients which served as controls (NN, n = 11). The differentially methylated regions (DMRs) were identified by DMRseq. Correlation analysis was performed between DMRs and their nearest differentially expressed genes (DEGs). Principal component analysis (PCA) was performed based on correlated DMR regulated genes. DMR regulated genes then were functional annotated. Cell-type deconvolutions were performed based on methylation levels. The comparisons revealed a total of 38 methylation-regulated genes in inactive UC that are potentially regulated by DMRs (correlation p value < 0.1). Several methylation-regulated genes could be identified in inactive UC participating in IL-10 and cytokine signalling pathways such as IL1B and STAT3. DNA methylation events in inactive UC seem to be fine-tuned by the balancing pro- and anti- inflammatory pathways to maintain a prevailed healing process to restore dynamic epithelium homeostasis.

Methylation-Regulated Long Non-Coding RNA Expression in Ulcerative Colitis

Long non-coding RNAs (lncRNAs) have been shown to play a role in the pathogenesis of ulcerative colitis (UC). Although epigenetic processes such as DNA methylation and lncRNA expression are well studied in UC, the importance of the interplay between the two processes has not yet been fully explored. It is, therefore, believed that interactions between environmental factors and epigenetics contribute to disease development. Mucosal biopsies from 11 treatment-naïve UC patients and 13 normal controls were used in this study. From each individual sample, both whole-genome bisulfite sequencing data (WGBS) and lncRNA expression data were analyzed. Correlation analysis between lncRNA expression and upstream differentially methylated regions (DMRs) was used to identify lncRNAs that might be regulated by DMRs. Furthermore, proximal protein-coding genes associated with DMR-regulated lncRNAs were identified by correlating their expression. The study identified UC-associated lncRNAs such as MIR4435-2HG, ZFAS1, IL6-AS1, and Pvt1, which may be regulated by DMRs. Several genes that are involved in inflammatory immune responses were found downstream of DMR-regulated lncRNAs, including SERPINB1, CCL18, and SLC15A4. The interplay between lncRNA expression regulated by DNA methylation in UC might improve our understanding of UC pathogenesis.

Anti-apoptotic genes and non-coding RNAs are potential outcome predictors for ulcerative colitis

Due to the lack of clinical, immunologic, genetic, and laboratory markers to predict remission in ulcerative colitis (UC) without relapse, there is no clear recommendation regarding withdrawal of therapy. Therefore, this study was to investigate if transcriptional analysis together with Cox survival analysis might be able to reveal molecular markers that are specific for remission duration and outcome. Mucosal biopsies from patients in remission with active treatment-naïve UC and healthy control subjects underwent whole-transcriptome RNA-seq. Principal component analysis (PCA) and Cox proportional hazards regression analysis were applied to the remission data concerning duration and status of patients. A randomly chosen remission sample set was used for validation of the applied methods and results. The analyses distinguished two different UC remission patient groups with respect to remission duration and outcome (relapse). Both groups showed that altered states of UC with quiescent microscopic disease activity are still present. The patient group with the longest remission duration and no relapse revealed specific and increased expression of antiapoptotic factors belonging to the MTRNR2-like gene family and non-coding RNAs. In summary, the expression of anti-apoptotic factors and non-coding RNAs may contribute to personalized medicine approaches in UC by improving patient stratification for different treatment regimens.

Associations of breast cancer related exposures and gene expression profiles in normal breast tissue-The Norwegian Women and Cancer normal breast tissue study

BACKGROUND

Normal breast tissue is utilized in tissue-based studies of breast carcinogenesis. While gene expression in breast tumor tissue is well explored, our knowledge of transcriptomic signatures in normal breast tissue is still incomplete. The aim of this study was to investigate variability of gene expression in a large sample of normal breast tissue biopsies, according to breast cancer related exposures (obesity, smoking, alcohol, hormone therapy, and parity).

METHODS

We analyzed gene expression profiles from 311 normal breast tissue biopsies from cancer-free, post-menopausal women, using Illumina bead chip arrays. Principal component analysis and K-means clustering was used for initial analysis of the dataset. The association of exposures and covariates with gene expression was determined using linear models for microarrays.

RESULTS

Heterogeneity of the breast tissue and cell composition had the strongest influence on gene expression profiles. After adjusting for cell composition, obesity, smoking, and alcohol showed the highest numbers of associated genes and pathways, whereas hormone therapy and parity were associated with negligible gene expression differences.

CONCLUSION

Our results provide insight into associations between major exposures and gene expression profiles and provide an informative baseline for improved understanding of exposure-related molecular events in normal breast tissue of cancer-free, post-menopausal women.

Identifying predictive signalling networks for Vedolizumab response in ulcerative colitis

BACKGROUND

In ulcerative colitis (UC), the molecular mechanisms that drive disease development and patient response to therapy are not well understood. A significant proportion of patients with UC fail to respond adequately to biologic therapy. Therefore, there is an unmet need for biomarkers that can predict patients' responsiveness to the available UC therapies as well as ascertain the most effective individualised therapy. Our study focused on identifying predictive signalling pathways that predict anti-integrin therapy response in patients with UC.

METHODS

We retrieved and pre-processed two publicly accessible gene expression datasets (GSE73661 and GSE72819) of UC patients treated with anti-integrin therapies: (1) 12 non-IBD controls and 41 UC patients treated with Vedolizumab therapy, and (2) 70 samples with 58 non-responder and 12 responder UC patient samples treated with Etrolizumab therapy without non-IBD controls. We used a diffusion-based signalling model which is mainly focused on the T-cell receptor signalling network. The diffusion model uses network connectivity between receptors and transcription factors.

RESULTS

The network diffusion scores were able to separate VDZ responder and non-responder patients before treatment better than the original gene expression. On both anti-integrin treatment datasets, the diffusion model demonstrated high predictive performance for discriminating responders from non-responders in comparison with 'nnet'. We have found 48 receptor-TF pairs identified as the best predictors for VDZ therapy response with AUC ≥ 0.76. Among these receptor-TF predictors pairs, FFAR2-NRF1, FFAR2-RELB, FFAR2-EGR1, and FFAR2-NFKB1 are the top best predictors. For Etrolizumab, we have identified 40 best receptor-TF pairs and CD40-NFKB2 as the best predictor receptor-TF pair (AUC = 0.72). We also identified subnetworks that highlight the network interactions, connecting receptors and transcription factors involved in cytokine and fatty acid signalling. The findings suggest that anti-integrin therapy responses in cytokine and fatty acid signalling can stratify UC patient subgroups.

CONCLUSIONS

We identified signalling pathways that may predict the efficacy of anti-integrin therapy in UC patients and personalised therapy alternatives. Our results may lead to the advancement of a promising clinical decision-making tool for the stratification of UC patients.

Profiling the T Cell Receptor Alpha/Delta Locus in Salmonids

In jawed vertebrates, two major T cell populations have been characterized. They are defined as α/β or γ/δ T cells, based on the expressed T cell receptor. Salmonids (family Salmonidae) include two key teleost species for aquaculture, rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar) which constitute important models for fish immunology and important targets for vaccine development. The growing interest to decipher the dynamics of adaptive immune responses against pathogens or vaccines has resulted in recent efforts to sequence the immunoglobulin (IG) or antibodies and T cell receptor (TR) repertoire in these species. In this context, establishing a comprehensive and coherent locus annotation is the fundamental basis for the analysis of high-throughput repertoire sequencing data. We therefore decided to revisit the description and annotation of TRA/TRD locus in Atlantic salmon and two strains of rainbow trout (Swanson and Arlee) using the now available high-quality genome assemblies. Phylogenetic analysis of functional TRA/TRD V genes from these three genomes led to the definition of 25 subgroups shared by both species, some with particular feature. A total of 128 TRAJ genes were identified in Salmo, the majority with a close counterpart in Oncorhynchus. Analysis of expressed TRA repertoire indicates that most TRAV gene subgroups are expressed at mucosal and systemic level. The present work on TRA/TRD locus annotation along with the analysis of TRA repertoire sequencing data show the feasibility and advantages of a common salmonid TRA/TRD nomenclature that allows an accurate annotation and analysis of high-throughput sequencing results, across salmonid T cell subsets.

Identifying anti-TNF response biomarkers in ulcerative colitis using a diffusion-based signalling model

Motivation

Resistance to anti-TNF therapy in subgroups of ulcerative colitis (UC) patients is a major challenge and incurs significant treatment costs. Identification of patients at risk of nonresponse to anti-TNF is of major clinical importance. To date, no quantitative computational framework exists to develop a complex biomarker for the prognosis of UC treatment. Modelling patient-wise receptor to transcription factor (TF) network connectivity may enable personalized treatment.

Results

We present an approach for quantitative diffusion analysis between receptors and TFs using gene expression data. Key TFs were identified using pandaR. Network connectivities between immune-specific receptor-TF pairs were quantified using network diffusion in UC patients and controls. The patient-specific network could be considered a complex biomarker that separates anti-TNF treatment-resistant and responder patients both in the gene expression dataset used for model development and separate independent test datasets. The model was further validated in rheumatoid arthritis where it successfully discriminated resistant and responder patients to tocilizumab treatment. Our model may contribute to prognostic biomarkers that may identify treatment-resistant and responder subpopulations of UC patients.

Availability and implementation

Software is available at https://github.com/Amy3100/receptor2tfDiffusion.

Supplementary information

Supplementary data are available at Bioinformatics Advances online.

DNA hypo-methylation facilitates anti-inflammatory responses in severe ulcerative colitis

Severe ulcerative colitis (UC) is a potentially life-threatening disease with a potential colorectal cancer (CRC) risk. The aim of this study was to explore the relationship between transcriptomic and genome-wide DNA methylation profiles in a well-stratified, treatment-naïve severe UC patient population in order to define specific epigenetic changes that could be responsible for the grade of disease severity. Mucosal biopsies from treatment-naïve severe UC patients (n = 8), treatment-naïve mild UC (n = 8), and healthy controls (n = 8) underwent both whole transcriptome RNA-Seq and genome-wide DNA bisulfite- sequencing, and principal component analysis (PCA), cell deconvolutions and diverse statistical methods were applied to obtain a dataset of significantly differentially expressed genes (DEGs) with correlation to DNA methylation for severe UC. DNA hypo-methylation correlated with approximately 80% of all DEGs in severe UC when compared to mild UC. Enriched pathways of annotated hypo-methylated genes revealed neutrophil degranulation, and immuno-regulatory interactions of the lymphoid system. Specifically, hypo-methylated anti-inflammatory genes found for severe UC were IL10, SIGLEC5, CD86, CLMP and members of inflammasomes NLRP3 and NLRC4. Hypo-methylation of anti-inflammatory genes during severe UC implies an interplay between the epithelium and lamina propria in order to mitigate inflammation in the gut. The specifically DNA hypo-methylated genes found for severe UC can potentially be useful biomarkers for determining disease severity and in the development of new targeted treatment strategies for severe UC patients.

Transcriptional Signatures That Define Ulcerative Colitis in Remission

BACKGROUND

This study addresses whether existing specific transcriptional profiles can improve and support the current status of the definition of ulcerative colitis (UC) remission apart from the existing endoscopic, histologic, and laboratory scoring systems. For that purpose, a well-stratified UC patient population in remission was compared to active UC and control patients and was investigated by applying the next-generation technology RNA-Seq.

METHODS

Mucosal biopsies from patients in remission (n = 14), patients with active UC (n = 14), and healthy control patientss (n = 16) underwent whole-transcriptome RNA-Seq. Principal component analysis, cell deconvolution methods, gene profile enrichment, and pathway enrichment methods were applied to define a specific transcriptional signature of UC in remission.

RESULTS

Analyses revealed specific transcriptional signatures for UC in remission with increased expression of genes involved in O-glycosylation (MUC17, MUC3A, MUC5AC, MUC12, SPON1, B3GNT3), ephrin-mediated repulsion of cells (EFNB2E, EFNA3, EPHA10, EPHA1), GAP junction trafficking (TUBA1C, TUBA4A, TUBB4B, GJB3, CLTB), and decreased expression of several toll-like receptors (TLR1, TLR3, TLR5, TLR6).

CONCLUSIONS

This study reveals specific transcriptional signatures for remission. Partial restoration and improvement of homeostasis in the epithelial mucus layer and revival of immunological functions were observed. A clear role for bacterial gut flora composition can be implied. The results can be useful for the development of treatment strategies for UC in remission and may be useful targets for further investigations aiming to predict the outcome of UC in the future.

Genome-wide DNA Methylation in Treatment-naïve Ulcerative Colitis

BACKGROUND AND AIMS

The aim of this study was to investigate the genome-wide DNA methylation status in treatment-naïve ulcerative colitis [UC], and to explore the relationship between DNA methylation patterns and gene expression levels in tissue biopsies from a well-stratified treatment-naïve UC patient group.

METHODS

Mucosal biopsies from treatment-naïve patients [n = 10], and a healthy control group [n = 11] underwent genome-wide DNA bisulfite sequencing. Principal component analysis [PCA] and diverse statistical methods were applied to obtain a dataset of differentially methylated genes. DNA methylation annotation was investigated using the UCSC Genome Browser. Gene set enrichments were obtained using the Kyoto Encyclopaedia of Genes and Genomes [KEGG] and PANTHER.

RESULTS

Of all significantly differentially expressed genes [DEGs], 25% correlated with DNA methylation patterns; 30% of these genes were methylated at CpG sites near their transcription start site [TSS]. Hyper-methylation was observed for genes involved in homeostasis and defence, whereas hypo-methylation was observed for genes playing a role in immune response [i.e. chemokines and interleukins]. Of the differentially DNA methylated genes, 25 were identified as inflammatory bowel disease [IBD] susceptibility genes. Four genes [DEFFA6, REG1B, BTNL3, OLFM4] showed DNA methylation in the absence of known CpG islands.

CONCLUSIONS

Genome-wide DNA methylation analysis revealed distinctive functional patterns for hyper-and hypo-methylation in treatment-naïve UC. These distinct patterns could be of importance in the development and pathogenesis of UC. Further investigation of DNA methylation patterns may be useful in the development of the targeting of epigenetic processes, and may allow new treatment and target strategies for UC patients.

Transcriptomic Landscape of Treatment-Naïve Ulcerative Colitis

BACKGROUND AND AIMS

Ulcerative colitis [UC] is a chronic inflammatory disease that effects the gastrointestinal tract and is considered one of the most prominent and common forms of inflammatory bowel disease [IBD]. This study aimed to define and describe the entire transcriptomic landscape in a well-stratified, treatment-naïve UC patient population compared with control patients by using next-generation technology, RNA-Seq.

METHODS

Mucosal biopsies from treatment-naïve UC patients [n = 14], and healthy controls [n = 16] underwent RNA-Seq. Principal component analysis [PCA], cell deconvolution methods, and diverse statistical methods were applied to obtain and characterise a dataset of significantly differentially expressed genes [DEGs].

RESULTS

Analyses revealed 1480 significantly DEGs in treatment-naïve UC when compared with controls. Cell populations of monocytes, T cells, neutrophils, B cells/ lymphoid cells, and myeloid cells were increased during inflammation, whereas the fraction of epithelial cells were reduced in UC, which is reflected by the DEGs; 79 DEGs were identified as IBD susceptibility genes, and 58 DEGs were expressed in a gender-specific manner. MUC5B, REG3A, DEFA5, and IL33 might be considered as colorectal cancer [CRC] risk factors following UC in males. AQP9 together with CLDN2 may have a role regulating tissue-specific physiological properties in tight junctions in UC. An additional functional role for AQP9 in the synthesis and/or the function of mucus can be implied.

CONCLUSIONS

This study reveals new potential players in UC pathogenesis in general, and provides evidence for a gender-dependent pathogenesis for UC. These results can be useful for the development of personalised treatment strategies for UC in the future.

The impact of partial hepatectomy on oxidative state in the liver remnant - An in vivo swine model

Background

Previous studies on oxidative state after partial hepatectomy (PHx) report conflicting data on levels of glutathione (GSH) and are mainly presented in rodent models by methodology less sensitive than the present technologies. The current swine model presents GSH levels and the following genetic response post-PHx, utilizing an analytical platform more sensitive and precise than earlier available.

Method

Twelve pigs were randomized to a PHx- and a control group (n=6 in each). The PHx group had a 60% hepatectomy. Serial in vivo liver biopsies during 12 h of anaesthesia post-PHx were analyzed for GSH by liquid chromatography mass spectrometry (LC-MS/MS). Transcriptional alterations of genes (GS, GCLM, GCLC, GR, HGF, NFE2L2, TGFβ1) regulating GSH synthesis were measured by real-time PCR.

Results

No difference was detected between the GSH levels in the PHx- and the control group during the experiment (P=0.247). Still, decreased gene expression of GS (P=0.026) and NFE2L2 (P=0.014) the first nine hours, and a decrease of TGFβ1 (P=0.029) the first seven hours post-PHx was seen in the liver remnant.

Conclusion

The results show that the liver has an extended capacity to maintain GSH homeostasis during major stress and parenchymal loss, even at the early onset of such trauma. This observation was not explained by increased expression of key genes in GSH pathways. Consequently, the results indicate an inherent compensatory capacity to maintain GSH homeostasis in the reduced organ.

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The levels of Glutathione are maintained after a 60% hepatectomy in a swine study.

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Oxidative state is analyzed after partial hepatectomy using mass spectrometry.

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Glutathione is analyzed after partial hepatectomy using mass spectrometry.

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The liver has extended capacity to remain GSH homeostasis after partial hepatectomy.

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Glutathione in liver tissue is analyzed after partial hepatectomy in a swine model.

Prognostic value of the MicroRNA regulators Dicer and Drosha in non-small-cell lung cancer: co-expression of Drosha and miR-126 predicts poor survival

Background

Dicer and Drosha are important enzymes for processing microRNAs. Recent studies have exhibited possible links between expression of different miRNAs, levels of miRNA processing enzymes, and cancer prognosis. We have investigated the prognostic impact of Dicer and Drosha and their correlation with miR-126 expression in a large cohort of non-small cell lung cancer (NSCLC) patients. We aimed to find patient groups within the cohort that might have an advantage of receiving adjunctive therapies.

Methods

Dicer expression in the cytoplasm and Drosha expression in the nucleus were evaluated by manual immunohistochemistry of tissue microarrays (TMAs), including tumor tissue samples from 335 patients with resected stages I to IIIA NSCLC. In addition, in situ hybridizations of TMAs for visualization of miR-126 were performed. Kaplan–Meier analysis was performed, and the log-rank test via SPSS v.22 was used for estimating significance levels.

Results

In patients with normal performance status (ECOG = 0, n = 197), high Dicer expression entailed a significantly better prognosis than low Dicer expression (P = 0.024). Dicer had no significant prognostic value in patients with reduced performance status (ECOG = 1–2, n = 138). High Drosha expression was significantly correlated with high levels of the microRNA 126 (miR-126) (P = 0.004). Drosha/miR-126 co-expression had a significant negative impact on the disease-specific survival (DSS) rate (P < 0.001). Multivariate analyses revealed that the interaction Dicer*Histology (P = 0.049) and Drosha/miR-126 co-expression (P = 0.033) were independent prognostic factors.

Conclusions

In NSCLC patients with normal performance status, Dicer is a positive prognostic factor. The importance of Drosha as a prognostic factor in our material seems to be related to miR-126 and possibly other microRNAs.

Electronic supplementary material

The online version of this article (doi:10.1186/1472-6890-14-45) contains supplementary material, which is available to authorized users.

Plasma fatty acid ratios affect blood gene expression profiles--a cross-sectional study of the Norwegian Women and Cancer Post-Genome Cohort

High blood concentrations of n-6 fatty acids (FAs) relative to n-3 FAs may lead to a “physiological switch” towards permanent low-grade inflammation, potentially influencing the onset of cardiovascular and inflammatory diseases, as well as cancer. To explore the potential effects of FA ratios prior to disease onset, we measured blood gene expression profiles and plasma FA ratios (linoleic acid/alpha-linolenic acid, LA/ALA; arachidonic acid/eicosapentaenoic acid, AA/EPA; and total n-6/n-3) in a cross-section of middle-aged Norwegian women (n = 227). After arranging samples from the highest values to the lowest for all three FA ratios (LA/ALA, AA/EPA and total n-6/n-3), the highest and lowest deciles of samples were compared. Differences in gene expression profiles were assessed by single-gene and pathway-level analyses. The LA/ALA ratio had the largest impact on gene expression profiles, with 135 differentially expressed genes, followed by the total n-6/n-3 ratio (125 genes) and the AA/EPA ratio (72 genes). All FA ratios were associated with genes related to immune processes, with a tendency for increased pro-inflammatory signaling in the highest FA ratio deciles. Lipid metabolism related to peroxisome proliferator-activated receptor γ (PPARγ) signaling was modified, with possible implications for foam cell formation and development of cardiovascular diseases. We identified higher expression levels of several autophagy marker genes, mainly in the lowest LA/ALA decile. This finding may point to the regulation of autophagy as a novel aspect of FA biology which warrants further study. Lastly, all FA ratios were associated with gene sets that included targets of specific microRNAs, and gene sets containing common promoter motifs that did not match any known transcription factors. We conclude that plasma FA ratios are associated with differences in blood gene expression profiles in this free-living population, and that affected genes and pathways may influence the onset and progression of disease.

Cancer-associated fibroblasts from human NSCLC survive ablative doses of radiation but their invasive capacity is reduced

Background

Cancer-Associated Fibroblasts (CAFs) are significant components of solid malignancies and play central roles in cancer sustainability, invasion and metastasis. In this study we have investigated the invasive capacity and matrix remodelling properties of human lung CAFs after exposure to ablative doses of ionizing radiation (AIR), equivalent to single fractions delivered by stereotactic ablative radiotherapy (SART) for medically inoperable stage-I/II non-small-cell lung cancers.

Methods

CAFs were isolated from lung tumour specimens from 16 donors. Initially, intrinsic radiosensitivity was evaluated by checking viability and extent of DNA-damage response (DDR) at different radiation doses. The migrative and invasive capacities of CAFs were thereafter determined after a sub-lethal single radiation dose of 18 Gy. To ascertain the mechanisms behind the altered invasive capacity of cells, expression of matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs) were measured in the conditioned media several days post-irradiation, along with expression of cell surface integrins and dynamics of focal contacts by vinculin-staining.

Results

Exposing CAFs to 1 × 18 Gy resulted in a potent induction of multiple nuclear DDR foci (> 9/cell) with little resolution after 120 h, induced premature cellular senescence and inhibition of the proliferative, migrative and invasive capacity. AIR promoted MMP-3 and inhibited MMP-1 appearance to some extent, but did not affect expression of other major MMPs. Furthermore, surface expression of integrins α2, β1 and α5 was consistently enhanced, and a dramatic augmentation and redistribution of focal contacts was observed.

Conclusions

Our data indicate that ablative doses of radiation exert advantageous inhibitory effects on the proliferative, migratory and invasive capacity of lung CAFs. The reduced motility of irradiated CAFs might be a consequence of stabilized focal contacts via integrins.

Deciphering normal blood gene expression variation--The NOWAC postgenome study

There is growing evidence that gene expression profiling of peripheral blood cells is a valuable tool for assessing gene signatures related to exposure, drug-response, or disease. However, the true promise of this approach can not be estimated until the scientific community has robust baseline data describing variation in gene expression patterns in normal individuals. Using a large representative sample set of postmenopausal women (N = 286) in the Norwegian Women and Cancer (NOWAC) postgenome study, we investigated variability of whole blood gene expression in the general population. In particular, we examined changes in blood gene expression caused by technical variability, normal inter-individual differences, and exposure variables at proportions and levels relevant to real-life situations. We observe that the overall changes in gene expression are subtle, implying the need for careful analytic approaches of the data. In particular, technical variability may not be ignored and subsequent adjustments must be considered in any analysis. Many new candidate genes were identified that are differentially expressed according to inter-individual (i.e. fasting, BMI) and exposure (i.e. smoking) factors, thus establishing that these effects are mirrored in blood. By focusing on the biological implications instead of directly comparing gene lists from several related studies in the literature, our analytic approach was able to identify significant similarities and effects consistent across these reports. This establishes the feasibility of blood gene expression profiling, if they are predicated upon careful experimental design and analysis in order to minimize confounding signals, artifacts of sample preparation and processing, and inter-individual differences.

As a major defence and transport system, blood cells are capable of adjusting gene expression in response to various clinical, biochemical, and pathological conditions. Here, we expand our understanding about the nature and extent of variation in gene expression from blood among healthy individuals. Using a large representative sample of postmenopausal women (N = 286) in the Norwegian Women and Cancer (NOWAC) postgenome study, we investigated blood gene expression changes due to normal inter-individuality (age, body mass index, fasting status), and exposure variables (smoking, hormone therapy, and medication use) at proportions and levels found in real life situations. Host genes were found to vary by inter-individual (i.e. fasting, BMI) and exposure (i.e. smoking) factors, and these gene lists may be used as a basis for further hypothesis development. Our study also establishes the feasibility of blood gene expression profiling for disease prediction, diagnosis, or prognosis, but underscores the necessity of care in study design and analysis to account for inter-individual differences and confounding signals.

New specific molecular targets for radio-chemotherapy of rectal cancer

Patients with locally advanced rectal cancer often receive preoperative radio-chemotherapy (RCT). The mechanisms of tumour response to radiotherapy are not understood. The aim of this study was to identify the effects of RCT on gene expression in rectal tumour and normal rectal tissue. For that purpose tissue samples from 21 patients with resectable adenocarcinomas were collected for use in whole genome-microarray based gene expression analysis. A factorial experimental design allowed us to determine the effect of RCT on tumour tissue alone by removing the effect of radiation on normal tissue. This resulted in 1327 differentially expressed genes in tumour tissue with p<0.05. In addition to known markers for radio-chemotherapy, a Gene Set Enrichment Analysis (GSEA) showed a significant enrichment in gene sets associated with cell adhesion and leukocyte transendothelial migration. The profound change of cell adhesion molecule expression in rectal tumour tissue could either increase the risk of metastasis, or decrease the tumour's invasive potential.

Early effects of high concentrations of progesterone and mifepristone A gene expression study of endometrial cancer cells (Ishikawa)

Patients with endometrial hyperplasia representing preliminary stages of endometrial cancer have shown to respond to therapy in 100% of the cases when treated with levonorgestrel-impregnated intrauterine device. Anti-proliferative effect has also been reported after application of an anti-progestin impregnated intrauterine device which showed to induce endometrial atrophy. The intention of the present study was to obtain more information of novel therapeutic targets for hormonal treatment in endometrial hyperplasia and endometrial cancers. Gene expression of signaling pathways after stimulation of Ishikawa cells with high doses of progesterone (32 microM) or Mifepristone (32 microM) was performed. After using an oligo microarrays representing 24,650 human genes and 37,580 gene transcripts, 6154 genes remained after pre-processing and filtering. This resulted in a total of 993 up-regulated genes with 189 genes for progesterone and 255 genes for Mifepristone. The 550 down-regulated genes were distributed with 256 genes for progesterone, 127 genes for RU 486. The results showed that genes presenting the epidermal growth factor (EGF)/MAP-kinase pathway were significantly over-represented by progesterone treatment, whereas, by Mifepristone treatment genes involved in the p53 pathway were also up-regulated (data not shown). These genes may be interesting as potential new therapeutic targets in endometrial hyperplasia and endometrial cancer, as candidate genes for therapy response or as candidate markers for tumor progression.

Gene expression in endometrial cancer cells (Ishikawa) after short time high dose exposure to progesterone

The potent antiproliferative effect of progestins has been utilized in clinical regimens for treatment of endometrial proliferative disorders. The progestin infiltrated intrauterine device used as therapy for endometrial carcinoma as well as endometrial hyperplasia yields a hundred-fold increase of local progestin concentration in the endometrium compared to that of oral treatment. The genetic basis for the complex effects of high dose progestins and the different signalling pathways regulated by these genes have never been accurately surveyed. The aim of the present study was to determine the gene expression pattern in highly differentiated endometrial cancer cells (Ishikawa) after short time exposure to high progesterone doses. In eight independent experiments, cells were treated with progesterone (30microg/ml) for 4h and gene expression was compared to that of untreated cells, which served as controls. Microarray analysis revealed 247 differentially expressed genes of which 126 were up-regulated and 121 were down-regulated. Of these, 135 genes are known to be involved in biological processes like cell cycle, cell proliferation and differentiation, developmental processes, immune responses, intracellular protein traffic and transport. Our study shows that microarray analysis can detect relevant gene expression changes in endometrial cells treated with progestin, including those involved in several alternative transcriptional factors and signalling pathways. Many of the differentially expressed genes were not previously known to be affected by progesterone or have unknown biological functions. Characterization of these genes may give new insights into molecular responses to treatment with high progesterone doses. Alternative signalling pathways for progesterone, rather than the classical steroid receptors pathways are also suggested.

Intravascular release and urinary excretion of tissue factor pathway inhibitor during heparin treatment

Tissue-factor-pathway inhibitor is the principal regulator of tissue factor-induced coagulation. Heparin treatment mobilizes TFPI into the circulation and contributes to the anticoagulant effects of heparins. Previous studies have demonstrated a selective depletion of intravascular TFPI by unfractionated heparin (UFH) but not by low-molecular-weight heparin (LMWH). In this study we sought to investigate the time- and dose-dependent relationships between release of TFPI and lipoprotein lipase (LPL) in respons to UFH and LMWH and to investigate whether the selective depletion of TFPI by UFH but not by LMWH is related to differential urinary excretion of TFPI. Eight healthy males participated in an open crossover study in which participants were assigned to receive (1) continuous infusion of unfractionated heparin (UFH, 450 IU/kg/24 hr); (2) subcutaneous dalteparin, 100 IU/kg given twice at a 12-hr interval; (3) subcutaneous dalteparin, 200 IU/kg given once; or (4) saline-solution infusion. Similar dose-dependent mobilization of TFPI and lipoprotein lipase (LPL), another glucosaminoglycan (GAG)-anchored protein of the endothelial membrane, was observed after both subcutaneous and intravenous administration of heparins. However, UFH induced a more efficient release of both TFPI and LPL into plasma than did LMWH at equivalent anti-Xa levels, indicating molecular-weight dependence of the release reactions. However, LPL reached peak levels faster and was more rapidly cleared from the circulation than was TFPI, regardless of the treatment modality. Only trace amounts of TFPI were detected in the urine in a native form (38 kD). UFH and LMWH treatment reduced renal clearance of TFPI compared with the control regimen. Our findings suggest that displacement of TFPI from the endothelial-surface GAG is the main mechanism for TFPI release during heparin treatment in vivo and that differential urinary excretion of TFPI is not the explanation for selective depletion of TFPI during UFH treatment.

Desensitization of muscarinic receptors

When Chinese hamster ovary cells transfected with the gene for M(3)-muscarinic receptors were stimulated with carbachol continuously for 30 min, the response at the end of the stimulation period was about 20% of the early response (2-3 min after the start of the stimulation). Long-term treatment of the cells with phorbol ester abolished the response completely while desensitization was significantly reduced upon pre-treatment of the cells with GF109203X, antisense oligonucleotide against the alpha-isoform of protein kinase C and wortmannin. We conclude that in the Chinese hamster ovary expression system, desensitization of M(3)-muscarinic receptors is dependent on a fast feedback loop including the alpha-isoform of protein kinase C.

Distinct guanine nucleotide binding protein alpha-subunit receptor coupling in GH cell lines: effects of bromocriptine and hormones on effector enzyme modulation

The purpose of the present study was to elucidate how the dopamine agonist bromocriptine affected receptor-effector systems in GH cells by measuring adenylate cyclase (AC) and phospholipase C (PL-C) modulation in cell membrane preparations. To perturb the interaction between the receptor and G-protein, polyclonal antibodies reacting with the predicted C-terminal amino acid sequence of G-protein alpha-subunits were used. The effect of bromocriptine on secretagogue elicited prolactin (PRL) secretion from whole cells was also monitored. Bromocriptine inhibited the basal secretion of PRL in a dose dependent manner, and completely abolished both the thyroliberin (TRH) and the vasoactive intestinal peptide (VIP) stimulated PRL secretion in GH(3) cells. Maximal inhibitory effect on PRL egress elicited by both hormones was obtained at 10-50 microM of bromocriptine. Messenger RNAs for both the short and long form of the D(2) receptor (D(2)R) were demonstrated in all three GH cell lines using the RT-PCR technique, advocating that D(2)Rs are coupled to distinct G-proteins and, thus, probably being responsible for the observed effects of bromocriptine in these cell lines. Basal AC activity, as measured in membrane preparations of GH(3) cells, remained unaffected by bromocriptine treatment (10 microM), while TRH and VIP stimulated AC activities (175% and 350% of control values, respectively) were partially inhibited (by some 50%). This inhibitory effect of bromocriptine was completely and specifically abolished in the presence of an antiserum against G(i2)alpha. Basal PL-C activity was also unaffected by bromocriptine, while TRH stimulated PL-C activity (350% of control value) was inhibited by bromocriptine (10 microM) by approximately 50%. Immunoblocking of G(q/11)alpha, however, reduced the stimulatory effect of TRH on PL-C activation by some 65%, while an antiserum against G(o)alpha partly counteracted the inhibitory effect of bromocriptine (10 microM) on TRH stimulated PL-C activity. Thus, TRH dependent AC stimulation was counteracted by bromocriptine via G(i2). TRH activation of PL-C occurs via G(q/11), while inhibition by bromocriptine appears to involve G(o). These mechanisms probably account for the major part of the actions of bromocriptine, however, other not yet recognised intermediates may be involved.

Mutations in the carboxyl-terminal domain of phospholipase C-beta 1 delineate the dimer interface and a potential Galphaq interaction site

The carboxyl-terminal domain of phospholipase C-beta is required for its stimulation by Galpha(q) and for its Galpha(q)-specific GTPase-activating protein (GAP) activity. We subjected this domain to a combination of deletion and alanine/glycine scanning mutagenesis to detect mutations that would inhibit either responsiveness to G(q) or G(q) GAP activity. Most mutations that altered either response or GAP activity diminished both in parallel. Many of these mutations map at the interface at which the carboxyl-terminal domain was recently shown to form a dimer (Singer, A. U., et al. (2001) Nat. Struct. Biol., 9, 32-36). Most others clustered in an area that is a plausible Galpha(q) binding site. In addition, one mutation that differentially inhibited GAP activity relative to responsiveness to Galpha(q) mapped in this region at a location modeled to be in close contact with the switch II region of Galpha(q). This is the site at which RGS proteins are thought to exert their GAP activity. Last, a deletion mutation differentially inhibited the response of phospholipase C-beta1 to Galpha(q) without blocking GAP activity. Its location in the molecule suggests that moving the attachment point of the catalytic domain can disrupt its ability to be activated by Galpha(q).

Molecular mechanisms involved in gastrin-mediated regulation of cAMP-responsive promoter elements

In the present study, we explore the role of cAMP-responsive (CRE) promoter elements in gastrin-mediated gene activation. By using the minimal CRE promoter reporter plasmid, pCRELuc, we show that gastrin can activate CRE. This activation is blocked by H-89 and GF 109203x, which inhibit protein kinases A and C, respectively. Moreover, Ca(2+)-activated pathways seem to be involved, because the calmodulin inhibitor W-7 reduced gastrin-mediated activation of pCRELuc. Deletion of CRE from the c-fos promoter rendered this promoter completely unresponsive to gastrin, indicating that CRE plays a central role in c-fos transactivation. Interestingly, gastrin-induced expression of the inducible cAMP early repressor (ICER), a gene that is known to be regulated by CRE promoter elements, was not reduced by H-89, W-7, or GF 109203x. Furthermore, bandshift analyses indicated that the region of the ICER promoter containing the CRE-like elements CARE 3-4 binds transcription factors that are not members of the CRE-binding protein-CRE modulator protein-activating transcription factor, or CREB/CREM/ATF-1, family. Our results underline the significance of the CRE promoter element in gastrin-mediated gene regulation and indicate that a variety of signaling mechanisms are involved, depending on the CRE promoter context.

Activation of phospholipase C by cholecystokinin receptor subtypes with different G-protein-coupling specificities in hormone-secreting pancreatic cell lines

Phospholipase C (PLC) activity was investigated by stimulation of membrane preparations obtained from insulin (beta-TC3)-, somatostatin (Rin 1027-B2)-, and glucagon (INR1-G9)-producing pancreatic cell lines using the non-hydrolyzable GTP analogue GTPgammaS alone, the C-terminal octapeptide cholecystokinin (CCK-8), or gastrin. All compounds caused a significant 2- to 4.4-fold stimulation of PLC activity in the different cell lines, which was diminished by the non-hydrolyzable GDP analogue GDPbetaS. CCK receptor subtypes were characterized by radioligand binding experiments. High-affinity binding sites for tritiated CCK(A) receptor antagonist L-364,718 (K(d) = 0.24 nM) and tritiated CCK(B) receptor antagonist L-365,260 (K(d) = 0.13 nM) were only present in Rin 1027-B2 cells. High-affinity binding sites for both ligands were not found in beta-TC3 or INR1-G9 cells. Competition binding experiments with non-labeled CCK receptor antagonists CR 1505 (CCK(A) receptor-selective) and CR 2945 (CCK(B) receptor-selective), as well as microphysiometry experiments, resulted in the same receptor distribution. Reverse transcriptase-polymerase chain reaction confirmed the CCK receptor distribution pattern for Rin 1027-B2 cells, but in addition showed the existence of CCK(B) receptors in beta-TC3 cells. Immunoblocking experiments with C-terminal antibodies against different G-protein alpha-subunits demonstrated inhibition of CCK-stimulated PLC activity in beta-TC3 cells by G(q/11)alpha antiserum (70%), in Rin 1027-B2 cells by G(q/11)alpha antiserum (70%) and G(i)-3alpha antiserum (23%), and in INR1-G9 cells by G(q/11)alpha antiserum (60%) and G(o)alpha antiserum (45%). We conclude that CCK receptor subtypes with different G-protein-coupling specificities to PLC are present in the different hormone-secreting cells of the endocrine pancreas.

Heparin induces synthesis and secretion of tissue factor pathway inhibitor from endothelial cells in vitro

TFPI is a potent inhibitor of the extrinsic coagulation system constitutively synthesized by endothelial cells. A major portion of intravascular TFPI is stored associated with endothelial cells. and administration of unfractionated heparin (UFH) in vivo causes a prompt mobilization of TFPI into the circulation. The present study was conducted to investigate how UFH affected the synthesis, secretion and anticoagulant potency of TFPI in endothelial cells in vitro. A spontaneously transformed immortal endothelial cell line was used (ECV304). Stimulation of ECV304 cells with UFH caused a prompt dose-dependent (0-5 IU UFH/ml) release of TFPI to the medium accompanied by no change of TFPI at the surface membrane assessed by immunocytochemical methods. Northern blot analysis revealed two mRNA transcripts for TFPI with a molecular size of 1.4 kb and 4.4 kb, respectively. Stimulation of ECV304 cells for 24 hrs with various concentrations of UFH caused a dose-dependent increase of TFPI in the medium (6.2-29.6 ng/10(6) cells within the concentration range 0-10 IU/ml). A similar dose-dependent increase in the expression of both TFPI mRNA species was observed. Long-term incubation of ECV304 cells with 5.0 IU/ml UFH caused a 5-10 fold increase in the TFPI concentration accumulated in the medium over 48 hrs. The increased TFPI mRNA expression induced by UFH appeared already after 10 min, peaked after 2-4 hrs, remained augmented throughout the entire period of UFH exposure, and preceded the synthesis-dependent increase in TFPI release by 2-4 hrs. The procoagulant activity of the cells was downregulated by 36% and the contribution of TFPI to the anticoagulant potency of ECV304 cells was moderately increased after 24 hrs heparin stimulation. It is suggested that these mechanisms are of major importance for the anticoagulant function of heparins.

Carboxyl-terminal fragments of phospholipase C-beta1 with intrinsic Gq GTPase-activating protein (GAP) activity

Fragments of the approximately 50 kDa COOH-terminal region of phospholipase C-beta1 (PLC-beta1(1)), ranging in size from 14 to 38 kDa, were expressed in Escherichia coli, purified, and tested for their regulatory activities. As expected, none of the fragments had phospholipase activity. Several fragments, referred to as PLC tails, displayed GTPase-activating protein (GAP) activity for Gq, the G protein class that stimulates the PLC-betas in response to receptors. Gq GAP activity is characteristic of intact PLC-betas. In reconstituted phospholipid vesicles that contained purified Gq and m1 muscarinic cholinergic receptors, the most active tails increased agonist-stimulated, steady-state GTPase activity over 4-fold. Stimulation of steady-state GTPase by the tails depended on receptors for facilitation of GDP-GTP exchange, suggesting that the tails act by accelerating hydrolysis of bound GTP. In addition to intrinsic GAP activity, one tail with high GAP activity and others with low or minimal activity potentiated the GAP activity of intact PLC-beta1. Other tails inhibited PLC-beta1s GAP effect. Both intrinsic GAP activity and potentiation of the PLC-beta1 GAP effect were often biphasic, with maxima as low as 100 nM tail and declining activities at higher concentrations. Several tails inhibited either the phospholipase activity of PLC-beta1, its stimulation by Gq, or both. The tails thus define the region of PLC-beta1 that has Gq GAP activity and suggest a mechanism of action in which the COOH terminus of PLC-betas can interact with Gq and with other PLC-beta1 molecules.

Phospholipase C activation in rat pituitary adenoma (GH) cells

The presence of the pertussis toxin (PTX) insensitive GTP-binding proteins (C-proteins) G(q) alpha and/or G(11) alpha has been demonstrated in three different prolactin (PRL) and growth hormone (GH) producing pituitary adenoma cell lines. Immunoblocking of their coupling to hormone receptors indicates that G(q) and/or G(11) confer throliberin (TRH) responsive phospholipase C (PL-C) activity in these cells. The contention was substantiated by immunoprecipitation analyses showing that anti G(q)/11 alpha-sera coprecipitated PL-C activity. In essence, only G(q)/11 (but neither G(12) G(13) nor G(o)) seems to mediate the TRH-sensitive PL-C activity, while G(o) may be coupled to a basal or constitutive PL-C activity. Immunoblocking studies imply that the B gamma-complex also, to some extent, may stimulate GH(3) pituitary cell line PL-C activity. Finally, the steady state levels of G(q)/(11) alpha mRNA and protein were down regulated upon long term exposure of the GH(3) cells to TRH (but not to vasoactive intestinal peptide = VIP).

Direct effects of vitamin D3 analogues on G-protein mediated signalling systems in rat osteosarcoma cells and rat pituitary adenoma cells

In normal rats treated with 1,25(OH)2D3 or 24,25(OH)2D3, serum Ca2+, ALP, PRL and GH are significantly altered. In order to study the primary effect of vitamin D3 analogues on target organ function, rat UMR 106 osteosarcoma and GH3 pituitary adenoma cells in monolayer culture were exposed accordingly. Surprisingly, prolonged exposure of these cell lines to physiological levels of either 1,25(OH)2D3 or 24,25(OH)2D3 did not significantly affect the secretory parameters (ALP, PRL or GH) tested. However, 1,25(OH)2D3 exposure significantly reduced PTH- and Gpp(NH)p-elicited AC as well as Gpp(NH)p-stimulated PLC activities in the UMR 106 cells. These changes were accompanied by an increase and decrease in the membrane contents of the G-protein subunits G36 beta and Gq/11 alpha, respectively. In contrast, 24,25(OH)2D3 remained without significant biological effect on these signalling systems despite concomitantly augmented levels of G36 beta. TRH- and Gpp(NH)p-elicited PLC activities in the GH3 cells were significantly reduced by 1,25(OH)2D3 with a concurrent reduction in cellular amounts of Gq/11 alpha, however, 24,25(OH)2D3 did not significantly alter any signalling systems nor G-proteins analyzed. It is concluded that the osteoblastic and pituitary cell secretion of ALP, PRL and GH remain unaffected by the presence of 1,25(OH)2D3 and 24,25(OH)2D3, despite distinct alterations in components of G-protein mediated signalling pathways. Hence, other factors like ambient Ca2+ may be responsible for the perturbed secretory patterns of ALP and PRL seen in vitamin D3 treated rats.

G-proteins: implications for pathophysiology and disease

This article focuses on the involvement of G-proteins in neuroendocrine secretion, cell growth and phenotype alterations. The current concept of hormonal activation of the GTPase cycle, as well as the molecular diversity of G-proteins families and receptor*G-protein*effector coupling, are described. Also described are certain G-proteins as possible proto-oncogenes and how point mutations and frame shift mutations alter G-protein function and determine the characteristics of various endocrine diseases. The article outlines in detail how receptors and G-proteins interact in prolactin and growth-hormone-secreting pituicytes, how G-proteins are involved in the growth and differentiation of preadipocytes and osteoblasts. All in all, it seems that hormonal activation through G-proteins is modulated through direct intra- and inter-signalling system cross-talk at the plasma membrane level (short-term) and through interactions on the level of transcription (HREs) from tyrosine kinases, steroid-like hormones and metabolic pathways. Pharmacological intervention to treat diseases where G-proteins are involved should take both long and short-term regulatory phenomena into consideration.

Cell-specific expression and function of adenylyl cyclases in rat pituitary tumour cell lines

The present study demonstrates cell-specific distribution and describes distinct functional regulation of different adenylyl cyclases (AC, types I-VI) in rat pituitary cell tumor cell lines (GH12C1, GH3 and GH4C1 cells) and pituitary tissue. Northern-blot analysis revealed a distinct pattern of cell-specific expression of the different AC types; Ca2+/calmodulin (CaM)-insensitive AC type II was found in all cell lines tested except GH(1)2C1 cells. The Ca(2+)-inhibitable AC type VI was found in all cell types tested. We observed a lack of the Ca2+/CaM-sensitive AC type I in GH3 and GH4C1 cells. GH(1)2C1 cells exclusively contained both Ca2+/CaM-sensitive AC types I and III, the latter previously believed to be specific for olfactory tissue. An additional transcript of AC type III was found in rat brain and rat liver tissue. AC type IV, which is Ca2+/CaM insensitive, could be detected in the prolactin-producing GH3 and GH4C1 cells and pituitary tissue but not in growth-hormone-producing GH(1)2C1 cells. Basal and vasoactive-intestinal-peptide-(VIP)-releasing-hormone, somatostatin (SRIF) and thyrotropin-releasing-hormone (TRH)-modulation of AC activity was measured in the presence of 100 microM EGTA, anti-CaM serum (dilution 1:2000) or 10 microM trifluoroperazine. Antisera against guanine-nucleotide-binding protein (G-protein) alpha subunits (G(i)-2 alpha, Gs alpha) and beta subunits (G beta 35/36) and CaM were added for functional studies of the SRIF and VIP-modulated AC in GH(1)2C1 and GH3 cells. These experiments indicate that the VIP and the SRIF receptors are coupled to a Ca2+/CaM-sensitive AC in GH(1)2C1 cells, different from the AC involved in the regulation of cAMP levels in GH3 and GH4C1 cells. In addition, the beta gamma-complex is possibly able to modulate SRIF-inhibited AC activity by potentiating the inhibitory effect. The TRH receptor in GH3 and GH4C1 cells is coupled to a Ca2+/CaM-sensitive AC which is different from the already cloned forms of AC types I and III. We, therefore, conclude that hormone regulation of pituitary tumour cell functions differs between the GH cell lines, due to specific utilisation of AC types.

Cell-specific expression of Gq/11 protein and mRNA in rat seminiferous tubules

As part of a study to elucidate the involvement of G proteins in signal transduction in testicular cells, we have examined the cellular localization of Gq/11 within the seminiferous tubules. The somatic cells (Sertoli cells, peritubular cells) contain high amounts of both Gq/11 alpha mRNA and immunoreactive protein. In contrast, very low levels of these G proteins and the corresponding mRNAs are present in the germ cells (pachytene spermatocytes, round spermatids). Thus, in the germ cells, receptor-regulated inositol phospholipid hydrolysis is not likely to be regulated via Gq/11, but rather through the Go protein, which has been previously shown to be abundant in rat germ cells. Since the somatic cells are nearly devoid of Go, the Gpp(NH)p-stimulated phospholipase C in these cells is probably regulated by Gq and/or G11.

Modulation of G proteins and second messenger responsiveness by steroid hormones in GH3rat pituitary tumour cells

We have investigated the modulation of different G protein alpha- and beta-subunit levels in prolactin (PRL) and growth hormone producing rat pituitary adenoma cells (GH3 cells) in culture after prolonged exposure (6-48 h) to the steroid hormones 17 beta-oestradiol and dexamethasone. Gi-3 alpha- and G beta-subunits were the only G protein subunits which increased in response to 10(-6) M oestradiol (to approximately 150 and 200% of controls, respectively), while the other alpha-subunits investigated (Gs alpha, Gi-2 alpha and G(o) alpha) remained relatively unchanged. Thyroliberin (TRH)--and guanosine 5'-[beta gamma-imido]trisphosphate (Gpp(NH)p)-elicited adenylyl cyclase (AC) activities were reduced during 6-12 h of oestradiol treatment (by 60 and 20%, respectively), while the inhibitory effect of somatostatin (SRIF) increased by approximately 100%. Dexamethasone (10(-6) M) increased levels of the stimulatory G protein Gs alpha (to approximately 340%) and decreased levels of Gi-3 alpha (to 25%). After 48 h, the AC response to TRH was reduced by approximately 70%, whereas the effect of the other modulators remained close to controls. We conclude that G protein subunits in GH3 cells are subject to specific regulation by steroid hormones and that this may be important in the tuning of the responsiveness of PRL secretion to hormones in the in vivo situation.

'Cross-talk' between phospholipase C and adenylyl cyclase involves regulation of G-protein levels in GH3 rat pituitary cells

We have investigated the possibility that adenylyl cyclase (AC) activity and membrane protein levels of the alpha-subunits of the stimulatory and inhibitory G-proteins of AC (Gs alpha and G(i)-2 alpha) in cultured prolactin-producing rat pituitary adenoma cells (GH3 cells) are modulated by phospholipase C (PLC)-generated second messengers. Pretreatment of cells (6-48 h) with ionomycin (1 microM) or 1-oleoyl-2-acetylglycerol (OAG; 1 microM) showed that ionomycin regulated Gs alpha levels in a time-dependent, biphasic manner; a two-fold increase followed a 40% initial reduction, while OAG lowered Gs alpha levels by more than 50% at all time-points. G(i)-2 alpha levels remained unchanged by both pretreatments. OAG, but not ionomycin, increased basal AC activity without increasing enzyme protein levels. Alterations in AC responsiveness to peptide hormones (e.g. thyroliberin and vasoactive intestinal peptide) correlated to membrane Gs protein alpha-subunit content. These results demonstrate the involvement of G-protein translation regulation as one mechanism of 'cross-talk' between the PLC- and AC-dependent signalling pathways.

Hypothalamic hormones modulate G protein levels and second messenger responsiveness in GH3 rat pituitary tumour cells

Thyroliberin (TRH), vasoactive intestinal peptide (VIP) and somatostatin (SRIF) act through receptors that are coupled to guanine nucleotide-binding regulatory proteins (G proteins). Regulation of hormone action may occur at the level of G protein coupling to the receptor or effector systems. In this study we demonstrate that prolonged exposure (for up to 48 hr) of cultured rat pituitary adenoma GH3 cells to these hormones caused homologous and to some extent heterologous attenuation of the adenylyl cyclase (AC) (EC 4.6.1.1) responsiveness. In addition, TRH and SRIF diminished both TRH- and guanosine 5'-[beta gamma-imido]-triphosphate-enhanced phospholipase C (PLC) (EC 3.1.4.3) activity within the same time-course. Measurements of cells membrane levels of Gs protein alpha-subunit (Gs alpha), G(i)-1 alpha/G(i)-2 alpha, G(i)-3 alpha, G(o) alpha and G beta by immunoblotting were performed. TRH and VIP upregulated levels of all G proteins except G(o) alpha and G beta. In contrast, SRIF caused a marked reduction of G beta levels. Thus, TRH and VIP, both acting through Gs, both modulated the alpha-subunit levels of this signal transducer, whereas SRIF, which possibly acts through G(i)-2, did not change the steady state level of G(i)-2 alpha. The actions of TRH, VIP and SRIF are multifaceted at the G protein level, where modulations of subtypes not directly involved in their actions may occur. These findings emphasize the complexity expected to be found in the in vivo situation.

The thyroliberin receptor interacts directly with a stimulatory guanine-nucleotide-binding protein in the activation of adenylyl cyclase in GH3 rat pituitary tumour cells. Evidence obtained by the use of antisense RNA inhibition and immunoblocking of the stimulatory guanine-nucleotide-binding protein

The thyroliberin receptor in GH3 pituitary tumour cells is known to couple to phospholipase C via a guanine-nucleotide-binding protein (G protein). Thyroliberin is postulated also to activate adenylyl cyclase, via the stimulatory G protein (Gs). In order to study this coupling, we constructed an antisense RNA expression vector that contained part of the Gs alpha-subunit cDNA clone (Gs alpha) in an inverted orientation relative to the mouse metallothionein promoter. The cDNA fragment included part of the coding region and all of the 3' non-translated region. Transient expression of Gs alpha antisense RNA in GH3 cells resulted in the specific decrease of Gs alpha mRNA levels, followed by decreased Gs alpha protein levels. Thyroliberin-elicited adenylyl cyclase activation in membrane preparations showed a reduction of up to 85%, whereas phospholipase C stimulation remained unaffected. Activation of adenylyl cyclase by vasoactive intestinal peptide was reduced by 30-40%. Investigation of the effects of thyroliberin and vasoactive intestinal peptide on adenylyl cyclase in GH3 cell membranes pretreated with antisera against Gs alpha and Gi-1 alpha/Gi-2 alpha support the results obtained by the use of the antisense technique. We conclude that thyroliberin has a bifunctional effect on GH3 cells, in activating adenylyl cyclase via Gs or a Gs-like protein in addition to the coupling to phospholipase C.

Regulation of G protein mRNA levels by thyroliberin, vasoactive intestinal peptide and somatostatin in prolactin-producing rat pituitary adenoma cells

We have investigated the regulation of mRNA levels of alpha- and beta-subunits of guanine nucleotide-binding regulatory proteins (G proteins) by peptide hormones in prolactin producing rat pituitary adenoma cells (GH3 cells) in culture. The cells were treated with thyroliberin (1 microM), vasoactive intestinal peptide (1 microM) or somatostatin (10 microM) for 6 to 48 hours. Thyroliberin and vasoactive intestinal peptide increased the levels of Gs alpha Go alpha, Gi-2 alpha, Gi-3 alpha, Gx alpha, G beta 36 and mRNAs. The effect of vasoactive intestinal peptide was however earlier and more pronounced. Gi-2 alpha mRNA levels showed the quantitatively largest alterations. Somatostatin upregulated Gs alpha and downregulated Go alpha and Gi-2 mRNAs. G protein mRNAs for Gi-2 alpha and Go alpha were increased by exposure of the cells to a medium devoid of serum. We conclude that G protein mRNA levels are subjected to alterations by hormones that act through the corresponding G proteins in the regulation of prolactin synthesis and secretion.

Cell-specific expression of guanine nucleotide-binding proteins in rat testicular cells

Guanine nucleotide-binding proteins (G proteins) are key components in membrane signal transduction that may play an important role in testis function. The present study is the first description of cell-specific differences in the contents of G protein alpha-subunits and their mRNAs in isolated rat testicular cells (pachytene spermatocytes, round spermatids, Sertoli cells, peritubular cells). By using Western blot techniques G1-3 alpha was shown to be the only pertussis toxin (PTX) substrate present in all the testicular cells examined. Surprisingly, we observed a lack of immunoreactive Gi-1 alpha/Gi-2 alpha protein in pachytene spermatocytes and round spermatids in spite of significant levels of the corresponding mRNAs as revealed by Northern analysis. No immunoreactive Gs alpha was detected in germ cells, in agreement with previous findings that the hormone-sensitive adenylyl cyclase is absent in these cell types. Peritubular cells and Sertoli cells contained no Go alpha, whereas high levels of both immunoreactive protein and mRNA were found in pachytene spermatocytes. This indicates that the Go protein may play a role at this stage of spermatogenesis. The stimulation of phospholipase C (PLC) in germ cell membranes by 5'-guanylyl imidophosphate indicates that PTX-sensitive PLC activation may be mediated by Go alpha or Gi-3 alpha.

Cell specific distribution of guanine nucleotide-binding regulatory proteins in rat pituitary tumour cell lines

To investigate the effects of guanine nucleotide-binding regulatory proteins (G proteins) on hormonal regulation of prolactin (PRL) synthesis and secretion, the qualitative distribution of G protein alpha-subunits and their mRNAs was studied in three functionally different pituitary tumour cell lines (GH cells) and normal rat pituitary tissue. Levels of basal and modulated adenylyl cyclase (AC) and phospholipase C (PLC) activities are also included. GH cells and pituitary tissue contained various amounts of mRNAs and protein for Gs alpha, Gi-2 alpha, Gi-3 alpha and Go alpha, while mRNA for Gi-1 alpha was only detected in normal pituitary tissue. Gz alpha/Gx alpha mRNA was expressed in all pituitary cell lines as well as in pituitary tissue. Go alpha mRNA and Gz alpha/G x alpha mRNA displayed size heterogeneity. These findings may have importance in the understanding of hormone regulation of second messenger systems.

Electroporation of rat pituitary (GH) cell lines: optimal parameters and effects on endogenous hormone production

An efficient electroporation procedure was established for the genetic transformation of two clonal strains of hormone producing rat pituitary cells (GH12C1 and GH3). We used the bacterial chloramphenicol acetyltransferase (CAT) gene as reporter gene to determine optimal conditions for electroporation. The conditions found to be optimal, measured as expression of the highest CAT activity, were 240-300 V and a DNA concentration of 30-60 micrograms/ml in sucrose buffer. Cell viability was then about 50 per cent. Maximum CAT activity was seen 24 hours after electroporation. The electroporation procedure, in the presence or absence of DNA, caused a transient decrease in endogenous growth hormone (GH) and prolactin (PRL) production.

Specific antisense RNA inhibition of growth hormone production in differentiated rat pituitary tumour cells

An expression vector that carried an inverted 800 base pair insert of the rat growth hormone (rGH) cDNA downstream of the SV40 promotor was used to transfect two different growth hormone (GH) producing rat pituitary cell strains, GH12C1 and GH3. This resulted in a specific transient inhibition of growth hormone production up to 75 percent in the course of 72 hours. GH synthesis reduction occurred parallel to a decrease of GH cytoplasmic mRNA levels. Levels of beta-actin and guanine nucleotide-binding regulatory protein (G protein) mRNAs were unaltered, but PRL mRNA levels were increased. Transfection with a control vector did not affect GH production.