Kinome-Wide Synthetic Lethal Screen Identifies PANK4 as a Modulator of Temozolomide Resistance in Glioblastoma

Temozolomide (TMZ) represents the cornerstone of therapy for glioblastoma (GBM). However, acquisition of resistance limits its therapeutic potential. The human kinome is an undisputable source of druggable targets, still, current knowledge remains confined to a limited fraction of it, with a multitude of under-investigated proteins yet to be characterized. Here, following a kinome-wide RNAi screen, pantothenate kinase 4 (PANK4) isuncovered as a modulator of TMZ resistance in GBM. Validation of PANK4 across various TMZ-resistant GBM cell models, patient-derived GBM cell lines, tissue samples, as well as in vivo studies, corroborates the potential translational significance of these findings. Moreover, PANK4 expression is induced during TMZ treatment, and its expression is associated with a worse clinical outcome. Furthermore, a Tandem Mass Tag (TMT)-based quantitative proteomic approach, reveals that PANK4 abrogation leads to a significant downregulation of a host of proteins with central roles in cellular detoxification and cellular response to oxidative stress. More specifically, as cells undergo genotoxic stress during TMZ exposure, PANK4 depletion represents a crucial event that can lead to accumulation of intracellular reactive oxygen species (ROS) and subsequent cell death. Collectively, a previously unreported role for PANK4 in mediating therapeutic resistance to TMZ in GBM is unveiled.

Schizosaccharomyces pombe Rtf2 is important for replication fork barrier activity of RTS1 via splicing of Rtf1

Arrested replication forks, when restarted by homologous recombination, result in error-prone DNA syntheses and non-allelic homologous recombination. Fission yeast RTS1 is a model fork barrier used to probe mechanisms of recombination-dependent restart. RTS1 barrier activity is entirely dependent on the DNA binding protein Rtf1 and partially dependent on a second protein, Rtf2. Human RTF2 was recently implicated in fork restart, leading us to examine fission yeast Rtf2's role in more detail. In agreement with previous studies, we observe reduced barrier activity upon rtf2 deletion. However, we identified Rtf2 to be physically associated with mRNA processing and splicing factors and rtf2 deletion to cause increased intron retention. One of the most affected introns resided in the rtf1 transcript. Using an intronless rtf1, we observed no reduction in RFB activity in the absence of Rtf2. Thus, Rtf2 is essential for correct rtf1 splicing to allow optimal RTS1 barrier activity.

BIOM-06. IDENTIFICATION OF AN INFLAMMATORY BIOMARKER SIGNATURE IN PLASMA-DERIVED EXTRACELLULAR VESICLES OF GLIOBLASTOMA PATIENTS

Diagnosis of Glioblastoma (GBM) remains a clinical challenge, currently relying on symptomatic presentation of the tumour, brain imaging and invasive biopsy. Description of effective biomarkers in biofluids could prove invaluable in GBM diagnosis. Extracellular vesicles (EVs) are essential to intercellular crosstalk in the tumour bulk and circulating EVs have been described as a potential reservoir of GBM biomarkers. Our work focuses on the: (i) isolation of EVs from blood liquid biopsies of GBM patients. (ii) Characterisation of their transcriptomic and proteomic cargoes to identify/validate novel candidate GBM biomarkers that could improve GBM diagnosis/prognosis. (iii) For cases where the original GBM tumour tissues are available, we will examine the expression of the identified biomarker signatures (derived from blood-EVs) to see if the content of EVs mirrors the transcriptomic/proteomic profile of the original tissue. Similar comparisons will be performed in GBM cohorts available in TCGA. Ultimately, in future studies, transcriptomic/proteomic analyses will be assessed during patients’ follow-ups to correlate the observed biomarker profiles with MRI data,treatment,recurrence, including molecular and clinical features.Our preliminary data comparing the proteomic cargoes of EVs derived from GBM patients (n=15) and those from healthy volunteers (n=10) indicated the presence of a GBM inflammatory biomarker signature comprising members of the complement and regulators of inflammation and coagulation. Bioinformatic analysis highlighted that all potential markers exclusively identified in patient samples have been linked with either GBM diagnosis,prognosis or associated signalling, suggesting that sEVs protein cargo could mirror the landscape of the original tumour and that selective circulating sEV-derived proteins might be used as hallmarks for GBM patients.Overall, this study is a step forward in the development of a non-invasive liquid biopsy approach for the identification of valuable biomarkers that could significantly improve GBM diagnosis and, consequently, patients’ prognosis and quality of life.

Molecular and functional characterization of an evolutionarily conserved CREB-binding protein in the Lymnaea CNS

In eukaryotes, CREB-binding protein (CBP), a coactivator of CREB, functions both as a platform for recruiting other components of the transcriptional machinery and as a histone acetyltransferase (HAT) that alters chromatin structure. We previously showed that the transcriptional activity of cAMP-responsive element binding protein (CREB) plays a crucial role in neuronal plasticity in the pond snail Lymnaea stagnalis. However, there is no information on the molecular structure and HAT activity of CBP in the Lymnaea central nervous system (CNS), hindering an investigation of its postulated role in long-term memory (LTM). Here, we characterize the Lymnaea CBP (LymCBP) gene and identify a conserved domain of LymCBP as a functional HAT. Like CBPs of other species, LymCBP possesses functional domains, such as the KIX domain, which is essential for interaction with CREB and was shown to regulate LTM. In-situ hybridization showed that the staining patterns of LymCBP mRNA in CNS are very similar to those of Lymnaea CREB1. A particularly strong LymCBP mRNA signal was observed in the cerebral giant cell (CGC), an identified extrinsic modulatory interneuron of the feeding circuit, the key to both appetitive and aversive LTM for taste. Biochemical experiments using the recombinant protein of the LymCBP HAT domain showed that its enzymatic activity was blocked by classical HAT inhibitors. Preincubation of the CNS with such inhibitors blocked cAMP-induced synaptic facilitation between the CGC and an identified follower motoneuron of the feeding system. Taken together, our findings suggest a role for the HAT activity of LymCBP in synaptic plasticity in the feeding circuitry.

Identification of an Inflammatory Biomarker Signature in Plasma-Derived Extracellular Vesicles of Glioblastoma Patients

AIMS

Description of effective biomarkers present in biofluids could prove invaluable in GBM diagnosis. Extracellular vesicles (EVs) are essential to intercellular crosstalk in the tumour bulk and circulating EVs have been described as a potential reservoir of GBM biomarkers. Therefore, EV-based liquid biopsies have been suggested as a promising tool for GBM

METHOD

Ethical approval was obtained for a prospective study of healthy donors and consenting GBM patients at the University Hospitals Sussex (Brighton). To identify GBM specific proteins, small EVs (sEVs) were isolated from plasma samples using differential ultracentrifugation and validated through Nanoparticles tracking analysis, transmission electron microscopy and detection of known sEVs markers such as CD9, CD63, CD81 and HSP70. sEVs content was characterised through mass spectrometry and bioinformatic tools.

RESULTS

Our data indicate the presence of a GBM inflammatory biomarker signature comprising members of the complement and regulators of inflammation and coagulation including VWF, FCGBP, C3, PROS1, and SERPINA1. Bioinformatic analysis highlighted that all potential markers exclusively identified in patient samples had already been linked with either GBM diagnosis, prognosis or associated signalling, suggesting that sEVs protein cargo could mirror the landscape of the original tumour and that selective circulating sEV-derived proteins might be used as hallmarks for GBM patients.

CONCLUSION

this study is a step forward in the development of a non-invasive liquid biopsy approach for the identification of valuable biomarkers that could significantly improve GBM diagnosis and, consequently, patients’ prognosis and quality of life.

A combined bioinformatics and LC-MS based approach for the development and benchmarking of a comprehensive database of Lymnaea CNS proteins

Applications of key technologies in biomedical research, such as qRT-PCR or LC-MS based proteomics, are generating large biological (-omics) data sets which are useful for the identification and quantification of biomarkers in any research area of interest. Genome, transcriptome and proteome databases are already available for a number of model organisms including vertebrates and invertebrates. However, there is insufficient information available for protein sequences of certain invertebrates, such as the great pond snail Lymnaea stagnalis, a model organism that has been used highly successfully in elucidating evolutionarily conserved mechanisms of memory function and dysfunction. Here we used a bioinformatics approach to designing and benchmarking a comprehensive CNS proteomics database (LymCNS-PDB) for the identification of proteins from the CNS of Lymnaea by LC-MS based proteomics. LymCNS-PDB was created by using the Trinity TransDecoder bioinformatics tool to translate amino acid sequences from mRNA transcript assemblies obtained from a published Lymnaea transcriptomics database. The blast-style MMSeq2 software was used to match all translated sequences to UniProtKB sequences for molluscan proteins, including Lymnaea and other molluscs. LymCNS-PDB contains 9,628 identified matched proteins that were benchmarked by performing LC-MS based proteomics analysis with proteins isolated from the Lymnaea CNS. MS/MS analysis using the LymCNS-PDB database led to the identification of 3,810 proteins. Only 982 proteins were identified by using a non-specific molluscan database. LymCNS-PDB provides a valuable tool that will enable us to perform quantitative proteomics analysis of protein interactomes involved in several CNS functions in Lymnaea, including learning and memory and age-related memory decline.

Combined Methylome, Transcriptome and Proteome Analyses Document Rapid Acclimatization of a Bacterium to Environmental Changes

Polynucleobacter asymbioticus strain QLW-P1DMWA-1^T represents a group of highly successful heterotrophic ultramicrobacteria that is frequently very abundant (up to 70% of total bacterioplankton) in freshwater habitats across all seven continents. This strain was originally isolated from a shallow Alpine pond characterized by rapid changes in water temperature and elevated UV radiation due to its location at an altitude of 1300 m. To elucidate the strain’s adjustment to fluctuating environmental conditions, we recorded changes occurring in its transcriptomic and proteomic profiles under contrasting experimental conditions by simulating thermal conditions in winter and summer as well as high UV irradiation. To analyze the potential connection between gene expression and regulation via methyl group modification of the genome, we also analyzed its methylome. The methylation pattern differed between the three treatments, pointing to its potential role in differential gene expression. An adaptive process due to evolutionary pressure in the genus was deduced by calculating the ratios of non-synonymous to synonymous substitution rates for 20 Polynucleobacter spp. genomes obtained from geographically diverse isolates. The results indicate purifying selection.

TMEM87a/Elkin1, a component of a novel mechanoelectrical transduction pathway, modulates melanoma adhesion and migration

Mechanoelectrical transduction is a cellular signalling pathway where physical stimuli are converted into electro-chemical signals by mechanically activated ion channels. We describe here the presence of mechanically activated currents in melanoma cells that are dependent on TMEM87a, which we have renamed Elkin1. Heterologous expression of this protein in PIEZO1-deficient cells, that exhibit no baseline mechanosensitivity, is sufficient to reconstitute mechanically activated currents. Melanoma cells lacking functional Elkin1 exhibit defective mechanoelectrical transduction, decreased motility and increased dissociation from organotypic spheroids. By analysing cell adhesion properties, we demonstrate that Elkin1 deletion is associated with increased cell-substrate adhesion and decreased homotypic cell-cell adhesion strength. We therefore conclude that Elkin1 supports a PIEZO1-independent mechanoelectrical transduction pathway and modulates cellular adhesions and regulates melanoma cell migration and cell-cell interactions.

When cells receive signals about their surrounding environment, this initiates a chain of signals which generate a response. Some of these signalling pathways allow cells to sense physical and mechanical forces via a process called mechanotransduction. There are different types of mechanotransduction. In one pathway, mechanical forces open up specialized channels on the cell surface which allow charged particles to move across the membrane and create an electrical current.

Mechanoelectrical transduction plays an important role in the spread of cancer: as cancer cells move away from a tumour they use these signalling pathways to find their way between cells and move into other parts of the body. Understanding these pathways could reveal ways to stop cancer from spreading, making it easier to treat. However, it remains unclear which molecules regulate mechanoelectrical transduction in cancer cells.

Now, Patkunarajah, Stear et al. have studied whether mechanoelectrical transduction is involved in the migration of skin cancer cells. To study mechanoelectrical transduction, a fine mechanical input was applied to the skin cancer cells whilst measuring the flow of charged molecules moving across the membrane. This experiment revealed that a previously unknown protein named Elkin1 is required to convert mechanical forces into electrical currents. Deleting this newly found protein caused skin cancer cells to move more slowly and dissociate more easily from tumour-like clusters of cells.

These findings suggest that Elkin1 is part of a newly identified mechanotransduction pathway that allows cells to sense mechanical forces from their surrounding environment. More work is needed to determine what role Elkin1 plays in mechanoelectrical transduction and whether other proteins are also involved. This could lead to new approaches that prevent cancer cells from dissociating from tumours and spreading to other body parts.

Amphiphilic nanogels: influence of surface hydrophobicity on protein corona, biocompatibility and cellular uptake

BACKGROUND AND PURPOSE

Nanogels (NGs) are promising drug delivery tools but are typically limited to hydrophilic drugs. Many potential new drugs are hydrophobic. Our study systematically investigates amphiphilic NGs with varying hydrophobicity, but similar colloidal features to ensure comparability. The amphiphilic NGs used in this experiment consist of a hydrophilic polymer network with randomly distributed hydrophobic groups. For the synthesis we used a new synthetic platform approach. Their amphiphilic character allows the encapsulation of hydrophobic drugs. Importantly, the hydrophilic/hydrophobic balance determines drug loading and biological interactions. In particular, protein adsorption to NG surfaces is dependent on hydrophobicity and critically determines circulation time. Our study investigates how network hydrophobicity influences protein binding, biocompatibility and cellular uptake.

METHODS

Biocompatibility of the NGs was examined by WST-1 assay in monocytic-like THP-1 cells. Serum protein corona formation was investigated using dynamic light scattering and two-dimensional gel electrophoresis. Proteins were identified by liquid chromatography-tandem mass spectrometry. In addition, cellular uptake was analyzed via flow cytometry.

RESULTS

All NGs were highly biocompatible. The protein binding patterns for the two most hydrophobic NGs were very similar to each other but clearly different from the hydrophilic ones. Overall, protein binding was increased with increasing hydrophobicity, resulting in increased cellular uptake.

CONCLUSION

Our study supports the establishment of structure-property relationships and contributes to the accurate balance between maximum loading capacity with low protein binding, optimal biological half-life and good biocompatibility. This is an important step to derive design principles of amphiphilic NGs to be applied as drug delivery vehicles.

Proteome Analysis of a M. avium Mutant Exposes a Novel Role of the Bifunctional Protein LysX in the Regulation of Metabolic Activity

Lysyl-phosphatidylglycerol is one of the components of the mycobacterial membrane that contributes to the resistance to cationic antimicrobial peptides, a host-induced frontline defense against invading pathogens. Its production is catalyzed by LysX, a bifunctional protein with lysyl transferase and lysyl transfer RNA synthetase activity. Comparative proteome analysis of a lysX mutant of Mycobacterium avium strain 104 and the wild type indicated that the lysX mutant strain undergoes a transition in phenotype by switching the carbon metabolism to β-oxidation of fatty acids, along with accumulation of lipid inclusions. Surprisingly, proteins associated with intracellular survival were upregulated in the lysX mutant, even during extracellular growth, preparing bacteria for the conditions occurring inside host cells. In line with this, the lysX mutant exhibited enhanced intracellular growth in human-blood-derived monocytes. Thus, our study exposes the significance of lysX in the metabolism and virulence of the environmental pathogen M. avium hominissuis.

Spatial UBE2N protein expression indicates genomic instability in colorectal cancers

BACKGROUND

One major hallmark of colorectal cancers (CRC) is genomic instability with its contribution to tumor heterogeneity and therapy resistance. To facilitate the investigation of intra-sample phenotypes and the de novo identification of tumor sub-populations, imaging mass spectrometry (IMS) provides a powerful technique to elucidate the spatial distribution patterns of peptides and proteins in tissue sections.

METHODS

In the present study, we analyzed an in-house compiled tissue microarray (n = 60) comprising CRCs and control tissues by IMS. After obtaining protein profiles through direct analysis of tissue sections, two validation sets were used for immunohistochemical evaluation.

RESULTS

A total of 28 m/z values in the mass range 800-3500 Da distinguished euploid from aneuploid CRCs (p < 0.001, ROC AUC values < 0.385 or > 0.635). After liquid chromatograph-mass spectrometry identification, UBE2N could be successfully validated by immunohistochemistry in the initial sample cohort (p = 0.0274, ROC AUC = 0.7937) and in an independent sample set of 90 clinical specimens (p = 0.0070, ROC AUC = 0.6957).

CONCLUSIONS

The results showed that FFPE protein expression profiling of surgically resected CRC tissue extracts by MALDI-TOF MS has potential value for improved molecular classification. Particularly, the protein expression of UBE2N was validated in an independent clinical cohort to distinguish euploid from aneuploid CRCs.

The RNA-binding protein ARPP21 controls dendritic branching by functionally opposing the miRNA it hosts

About half of mammalian miRNA genes lie within introns of protein-coding genes, yet little is known about functional interactions between miRNAs and their host genes. The intronic miRNA miR-128 regulates neuronal excitability and dendritic morphology of principal neurons during mouse cerebral cortex development. Its conserved host genes, R3hdm1 and Arpp21, are predicted RNA-binding proteins. Here we use iCLIP to characterize ARPP21 recognition of uridine-rich sequences with high specificity for 3′UTRs. ARPP21 antagonizes miR-128 activity by co-regulating a subset of miR-128 target mRNAs enriched for neurodevelopmental functions. Protein–protein interaction data and functional assays suggest that ARPP21 acts as a positive post-transcriptional regulator by interacting with the translation initiation complex eIF4F. This molecular antagonism is reflected in inverse activities during dendritogenesis: miR-128 overexpression or knockdown of ARPP21 reduces dendritic complexity; ectopic ARPP21 leads to an increase. Thus, we describe a unique example of convergent function by two products of a single gene.

Many microRNA encoding regions are within introns of other coding genes, and yet the molecular or functional interaction between the two is unclear. This study shows that miR-128′s function is opposed by its host gene ARPP21, and they have complementary effects on neuronal development.

APLP1 is endoproteolytically cleaved by γ-secretase without previous ectodomain shedding

Regulated intramembrane proteolysis of the amyloid precursor protein (APP) and its homologs, the APP like proteins APLP1 and APLP2, is typically a two-step process, which is initiated by ectodomain-shedding of the substrates by α- or β-secretases. Growing evidence, however, indicates that the cleavage process for APLP1 is different than for APP. Here, we describe that full-length APLP1, but not APP or APLP2, is uniquely cleaved by γ-secretase without previous ectodomain shedding. The new fragment, termed sAPLP1γ, was exclusively associated with APLP1, not APP, APLP2. We provide an exact molecular analysis showing that sAPLP1γ was uniquely generated by γ-secretase from full-length APLP1. Mass spectrometry analysis showed that the sAPLP1γ fragment and the longest Aβ-like peptide share the C-terminus. This novel mechanism of γ-secretase action is consistent with an ϵ-cut based upon the nature of the reaction in APP. We further demonstrate that the APLP1 transmembrane sequence is the critical determinant for γ-shedding and release of full-length APLP1. Moreover, the APLP1 TMS is sufficient to convert larger type-I membrane proteins like APP into direct γ-secretase substrates. Taken together, the direct cleavage of APLP1 is a novel feature of the γ-secretase prompting a re-thinking of γ-secretase activity modulation as a therapeutic strategy for Alzheimer disease.

Bioengineering of rFVIIa Biopharmaceutical and Structure Characterization for Biosimilarity Assessment

Eptacog alfa (NovoSeven^®) is a vitamin K-dependent recombinant Factor VIIa produced by genetic engineering from baby hamster kidney (BHK) cells as a single peptide chain of 406 residues. After activation, it consists of a light chain (LC) of 152 amino and a heavy chain (HC) of 254 amino acids. Recombinant FVIIa undergoes many post-translational modifications (PTMs). The first ten glutamic acids of the N-terminal moiety are γ-carboxylated, Asn145 and Asn322 are N-glycosylated, and Ser52 and Ser60 are O-glycosylated. A head-to-head biosimilarity study was conducted for the originator and the first biosimilar AryoSeven™ to evaluate comparable bioengineering. Physicochemical properties were analyzed based on mass spectrometry, including intact mass, PTMs and higher-order structure. Both biotherapeutics exhibit a batch-to-batch variability in their N-glycan profiles. N-Glycopeptide analysis with UHPLC-QTOF-MS^E confirmed N-glycosylation sites as well as two different O-glycopeptide sites. Ser60 was found to be O-fucosylated and Ser52 had O-glucose or O-glucose-(xylose)_1,2 motifs as glycan variants. Ion mobility spectrometry (TWIMS) and NMR spectroscopy data affirm close similarity of the higher-order structure of both biologicals. Potency of the biodrugs was analyzed by a coagulation assay demonstrating comparable bioactivity. Consequently, careful process optimization led to a stable production process of the biopharmaceuticals.

Antimicrobial defence and persistent infection in insects revisited

Insects show long-lasting antimicrobial immune responses that follow the initial fast-acting cellular processes. These immune responses are discussed to provide a form of phrophylaxis and/or to serve as a safety measure against persisting infections. The duration and components of such long-lasting responses have rarely been studied in detail, a necessary prerequisite to understand their adaptive value. Here, we present a 21 day proteomic time course of the mealworm beetle Tenebrio molitor immune-challenged with heat-killed Staphylococcus aureus The most upregulated peptides are antimicrobial peptides (AMPs), many of which are still highly abundant 21 days after infection. The identified AMPs included toll and imd-mediated AMPs, a significant number of which have no known function against S. aureus or other Gram-positive bacteria. The proteome reflects the selective arena for bacterial infections. The results also corroborate the notion of synergistic interactions in vivo that are difficult to model in vitroThis article is part of the themed issue 'Evolutionary ecology of arthropod antimicrobial peptides'.

Proteomic analysis reveals differential protein expression in variants of papillary thyroid carcinoma

Introduction

Fine Needle Aspiration Biopsy (FNAB) allows the cytological differentiation of benign and malignant thyroid nodules. However, the method itself is not adequate in determining some cases. For example, the diagnosis of Follicular Variant Papillary Thyroid Carcinoma (FV-PTC) can be challenging. In the current study we investigate the protein profiles of FV-PTC and classical variant PTC (CV-PTC) with no lymph node metastasis and compare it with benign thyroid tissue.

Method

We used CV-PTC (n = 6), FV-PTC (n = 6) and benign thyroid tissues (n = 6) to prepare tissue lysates. Proteins from each group were trypsin and lys-C digested. The samples were analyzed on a Q Exactive Orbitrap mass spectrometer.

Results

We identified 2560 proteins across all 18 specimens. Protein profiles revealed that there was no clear distinction between benign and FV-PTC samples. However, further examination of our data showed that proteins in energy metabolism have altered in FV-PTC. Proteomic pathway analysis showed marked alteration of the actin cytoskeleton proteins, especially several members of Arp2/3 complex were significantly increased in CV-PTC. We made the novel observation that IQGAP1 protein was significantly increased in CV-PTC, whereas IQGAP2 protein was highly expressed in FV-PTC lesions, suggesting differential roles of IQGAP proteins in thyroid pathology.

Conclusion

In the present study, mass spectrometry based label free quantification approach was applied to investigate the protein profiles of FV-PTC, CV-PTC and benign thyroid tissues. This study pointed out that actin cytoskeleton proteins, IQGAP proteins and changes in energy metabolism play predominant roles in thyroid pathology.

Mass spectrometry data from label-free quantitative proteomic analysis of harmless and pathogenic strains of infectious microalgae, Prototheca spp

Here, we provide the dataset associated with our research article 'label-free quantitative proteomic analysis of harmless and pathogenic strains of infectious microalgae, Prototheca spp.' (Murugaiyan et al., 2017) [1]. This dataset describes liquid chromatography-mass spectrometry (LC-MS)-based protein identification and quantification of a non-infectious strain, Prototheca zopfii genotype 1 and two strains associated with severe and mild infections, respectively, P. zopfii genotype 2 and Prototheca blaschkeae. Protein identification and label-free quantification was carried out by analysing MS raw data using the MaxQuant-Andromeda software suit. The expressional level differences of the identified proteins among the strains were computed using Perseus software and the results were presented in [1]. This DiB provides the MaxQuant output file and raw data deposited in the PRIDE repository with the dataset identifier PXD005305.

Alzheimer amyloid peptide aβ42 regulates gene expression of transcription and growth factors

The pathogenesis of Alzheimer's disease (AD) is characterized by the aggregation of amyloid-β (Aβ) peptides leading to deposition of senile plaques and a progressive decline of cognitive functions, which currently remains the main criterion for its diagnosis. Robust biomarkers for AD do not yet exist, although changes in the cerebrospinal fluid levels of tau and Aβ represent promising candidates in addition to brain imaging and genetic risk profiling. Although concentrations of soluble Aβ42 correlate with symptoms of AD, less is known about the biological activities of Aβ peptides which are generated from the amyloid-β protein precursor. An unbiased DNA microarray study showed that Aβ42, at sub-lethal concentrations, specifically increases expression of several genes in neuroblastoma cells, notably the insulin-like growth factor binding proteins 3 and 5 (IGFBP3/5), the transcription regulator inhibitor of DNA binding, and the transcription factor Lim only domain protein 4. Using qRT-PCR, we confirmed that mRNA levels of the identified candidate genes were exclusively increased by the potentially neurotoxic Aβ42 wild-type peptide, as both the less toxic Aβ40 and a non-toxic substitution peptide Aβ42 G33A did not affect mRNA levels. In vivo immunohistochemistry revealed a corresponding increase in both hippocampal and cortical IGFBP5 expression in an AD mouse model. Proteomic analyses of human AD cerebrospinal fluid displayed increased in vivo concentrations of IGFBPs. IGFBPs and transcription factors, as identified here, are modulated by soluble Aβ42 and may represent useful early biomarkers.

Caloric restriction and intermittent fasting alter hepatic lipid droplet proteome and diacylglycerol species and prevent diabetes in NZO mice

Caloric restriction and intermittent fasting are known to improve glucose homeostasis and insulin resistance in several species including humans. The aim of this study was to unravel potential mechanisms by which these interventions improve insulin sensitivity and protect from type 2 diabetes. Diabetes-susceptible New Zealand Obese mice were either 10% calorie restricted (CR) or fasted every other day (IF), and compared to ad libitum (AL) fed control mice. AL mice showed a diabetes prevalence of 43%, whereas mice under CR and IF were completely protected against hyperglycemia. Proteomic analysis of hepatic lipid droplets revealed significantly higher levels of PSMD9 (co-activator Bridge-1), MIF (macrophage migration inhibitor factor), TCEB2 (transcription elongation factor B (SIII), polypeptide 2), ACY1 (aminoacylase 1) and FABP5 (fatty acid binding protein 5), and a marked reduction of GSTA3 (glutathione S-transferase alpha 3) in samples of CR and IF mice. In addition, accumulation of diacylglycerols (DAGs) was significantly reduced in livers of IF mice (P=0.045) while CR mice showed a similar tendency (P=0.062). In particular, 9 DAG species were significantly reduced in response to IF, of which DAG-40:4 and DAG-40:7 also showed significant effects after CR. This was associated with a decreased PKCε activation and might explain the improved insulin sensitivity. In conclusion, our data indicate that protection against diabetes upon caloric restriction and intermittent fasting associates with a modulation of lipid droplet protein composition and reduction of intracellular DAG species.

Effects of thawing, refreezing and storage conditions of tissue samples and protein extracts on 2-DE spot intensity

We report that reliable quantitative proteome analyses can be performed with tissue samples stored at -80 degrees C for up to 10 years. However, storing protein extracts at 4 degrees C for 24 h and freezing protein extracts at -80 degrees C and thawing them significantly altered 41.6 and 17.5% of all spot intensities on 2-DE gels, respectively. Fortunately, these storing effects did not impair the reliability of quantifying 2-DE experiments. Nonetheless, the results show that freezing and storage conditions should be carefully controlled in proteomic experiments.

Improved comparative proteome analysis based on two-dimensional gel electrophoresis

The purpose of this study was to test the extent to which differences in spot intensity can be reliably recognized between two groups of two-dimensional electrophoresis gels (pH 4-7, visualized with ruthenium fluorescent stain) each loaded with different amounts of protein from rat brain (power analysis). Initial experiments yielded only unsatisfactory results: 546 spots were matched from two groups of 6 gels each loaded with 200 microg and 250 microg protein, respectively. Only 72 spots were higher (p<0.05), while 58 spots were significantly lower in the 250-microg group. The construction of new apparatuses that allowed the simultaneous processing of 24 gels throughout all steps between rehydration and staining procedure considerably lowered the between-gel variation. This resulted in the detection of significant differences in spot intensities in 77-90% of all matched spots on gel groups with a 25% difference in protein load. This applied both when protein from 24 biological replicates was loaded onto two groups of 12 gels and when two pooled tissue samples were each loaded onto 6 gels. At a difference of 50% in protein load, more than 90% of all spots differed significantly between two experimental groups.

Thyroid hormones in the rat amygdala as common targets for antidepressant drugs, mood stabilizers, and sleep deprivation

BACKGROUND

There have been repeated reports of antidepressant effects of thyroid hormones. In this study, we investigated whether antidepressant treatments enhance the concentrations of thyroid hormones in rat brain.

METHODS

Each of the groups of rats was treated for 14 days with one of the following: an antidepressant drug (desipramine, paroxetine, venlafaxine, or tianeptine); a mood stabilizer (lithium or carbamazepine); or 8 hours' partial sleep deprivation. Thyroid hormone concentrations were quantified in homogenates, nuclei, mitochondria, synaptosomes, myelin, and microsomes in 11 rat brain areas.

RESULTS

No drug effects were seen on nuclear triiodothyronine (T(3)) concentrations in any brain area. In the amygdala, all antidepressant drugs enhanced the levels of T(3) in the myelin fraction. Triiodothyronine molecules were identified in the myelin by immunogold labeling. Quantification of the major lipid components showed a selective decrease in cholesterol in the myelin of the amygdala after desipramine treatment. Desipramine induced an increase in protein concentrations, 3,5-diiodothyronine levels, and the activity of the mitochondrial enzyme succinate dehydrogenase in the mitochondria of the amygdala. Lithium, carbamazepine, and partial sleep deprivation raised the levels of T(3) in synaptosomes of the amygdala.

CONCLUSIONS

These results demonstrate that thyroid hormones in the amygdala are a common target of different antidepressant and mood-stabilizing therapies.

Effects of hyper- and hypothyroidism on thyroid hormone concentrations in regions of the rat brain

The purpose of this study was to investigate the effects of hyper- and hypothyroidism on thyroid hormone concentrations and deiodinase activities in nine regions of the rat brain. Four weeks of treatment with 75 microg thyroxine (T4)/kg body wt induced a two- to threefold increase in T4 levels in all of these brain regions, whereas the 3,5,3'-triiodothyronine (T3) concentrations were reduced in five brain regions and remained unchanged in four. Even after 8 wk treatment with 300 microg T4/kg, the T3 concentrations remained normal in cortical areas, the hippocampus and amygdala, and were elevated only in areas in which inner-ring deiodinase activity was low or absent, and in the hypothalamus. At the subcellular level, nuclear concentrations of T3 were diminished in hypothyroidism but remained unaltered in hyperthyroidism in all areas except the hypothalamus, where they were enhanced. Cortical mitochondrial succinate dehydrogenase activity was reduced in both hypo- and hyperthyroidism in spite of normal T3 concentrations in hyperthyroid animals. The results show that nuclear T3 concentrations fall in hypothyroidism but do not change during severe hyperthyroidism in any brain region except the hypothalamus. Further research is thus needed to clarify the mechanisms mediating the numerous biochemical and psychological effects of hyperthyroidism.

Concentrations of seven iodothyronine metabolites in brain regions and the liver of the adult rat

The concentrations of the iodothyronine metabolites T(4), T(3), 3,5-diiodothyronine (3,5-T(2)), 3,3'-diiodothyronine (3,3'-T(2)), reverse T(3) (rT(3)), 3,3'-T(2) sulfate (3,3'T(2)S), and T(3) sulfate (T(3)S) were measured in 12 regions of the brain, the pituitary gland, and liver in adult male rats. Quantification of iodothyronine was performed by RIA following a newly developed method of purification and separation by HPLC. 3,5-T(2), 3,3'-T(2), rT(3) and T(2)S were detectable in the low femtomolar range (20-200 fmol/g) in most areas of the rat brain. T(3)S was detectable only in the hypothalamus. The concentrations of T(3) and T(4) were approximately 20- to 60-fold higher, ranging between 1 and 6 pmol/g. There was a significant negative correlation between the activities of inner-ring deiodinase and T(3) concentrations across brain areas. In the liver, 3,5-T(2), rT(3), and T(3)S were measurable in the low femtomolar range, whereas 3,3'-T(2) and 3,3'T(2)S were not detectable. 3,5-T(2) and 3,3'-T(2) were not detectable in mitochondrial fractions of the brain regions. Tissue concentrations of 3,5-T(2) exhibited a circadian variation closely parallel to those of T(3) in the brain regions and liver. T(3) was not a substrate for outer-ring deiodination under different experimental conditions; thus, it remains unclear which substrate(s) and enzyme(s) are involved in the production of 3,5-T(2). These results indicate that five iodothyronine metabolites other than T(3) and T(4) are detectable in the low femtomolar range in the rat brain and/or liver. The physiological implications of this finding are discussed.

Gene expression of receptors and enzymes involved in GABAergic and glutamatergic neurotransmission in the CNS of rats behaviourally dependent on ethanol

The steady state levels of the messenger RNA (mRNA) of eight GABA(A) receptor subunits, five glutamate receptor subunits and seven enzymes involved in the synthesis of glutamate and GABA were measured in eight regions of rat brain in a recently developed animal model of 'behavioural dependence' on ethanol. 'Behavioural dependence' including loss of control was induced by offering the rats the choice between ethanol and water over a 9-month period (Group A). This group was compared with a group given the choice between ethanol and water for only 2 months (not yet 'behaviourally dependent', Group B), a group forced to consume ethanol as sole fluid over a 9-month period (also not 'behaviourally dependent', Group C) and ethanol-naive control rats (Group D). All groups were sacrificed 1 month after the ethanol was withdrawn. The mRNA concentrations of all eight GABA receptor subunits, four out of the five subunits of different glutamate receptors and those of seven enzymes involved in GABA and glutamate production were reduced almost exclusively in the parieto-occipital cortex in Groups A and B, but not Group C. These data suggest that the synthesis of glutamate and GABA and the activities of their respective neurons are selectively impaired in the parieto-occipital cortex in the groups having consumed ethanol in a free-choice design, in which its rewarding properties can better take effect than after forced administration. As the parieto-occipital cortex is believed to contain emotional memory structures, it may be hypothesized that the glutamatergic and GABAergic neuronal systems in this area are involved in the development of memory for reward from ethanol. However, they are not specifically associated with 'behavioural dependence'.

Effects of pharmacological and nonpharmacological treatments on thyroid hormone metabolism and concentrations in rat brain

The activities of the 5'I-deiodinase (5'D-I), 5'II deiodinase (5'D-II) and 5III-deiodinase (5D-III) isoenzymes and tissue concentrations of thyroxine (T4) and triiodothyronine (T3) were measured in up to 10 regions of the rat brain after acute and subchronic nonpharmacological (sleep deprivation, 12 h fasting, 14 days' calorie-reduced diet) and pharmacological (ethanol, haloperidol, clozapine, lithium, carbamazepine, desipramine, fluoxetine, tranylcypromine, and mianserin) treatments. All of these treatments induced significant and sometimes dramatic changes in 5'D-II activities and tissue concentrations of thyroid hormones and, to a lesser extent, in 5D-III activity. The activity of 5'D-I remained unaffected. The results revealed a surprising specificity for each type of treatment in terms of the isoenzyme and hormone affected, the direction of the change, the brain region affected and the time of day. The changes in thyroid hormone concentrations frequently failed to correspond in any way to those in deiodinase activities and unexpected effects such as inhibition of both 5'D-II and 5D-III were seen, indicating that there may be additional pathways of iodothyronine metabolism in the CNS. In conclusion, particularly 5'D-II activity and thyroid hormone concentrations in the CNS are highly sensitive to many different kinds of influence that may induce changes in neuronal activity. However, these changes in deiodinase activities do not ensure stable tissue concentrations of T3, but were, on the contrary, in most cases accompanied by marked changes T3 levels in the tissue. The implications of these findings for the physiological role of thyroid hormones in the CNS are discussed.

Effects of tranylcypromine on thyroid hormone metabolism and concentrations in rat brain

The effect of 14 days administration of the anti-depressant tranylcypromine (TCP) on iodothyronine deiodinase activities and the concentrations of thyroxine (T4) and triiodothyronine (T3) were investigated in homogenates of up to nine regions of the rat brain. The activity of the 5III deiodinase isoenzyme, which catalyses the inactivation of T3 to 3,3'-diiodothyronine (3,3'-T2), was enhanced in eight brain regions. However, the brain levels of T4 were completely unchanged and the T3 concentrations were significantly reduced in the frontal cortex only. Therefore, we also measured the T3 concentrations of three subcellular fractions (nuclei, synaptosomes and mitochondria) of six brain regions. TCP induced a significant reduction in T3 levels in the synaptosomes of the frontal cortex and significant increases in the mitochondrial T3 concentrations in the amygdala. The latter effect was replicated after 14 days administration of 5 mg/kg desipramine. No effects of either drug on nuclear concentrations of T3 were seen in any brain region. As the amygdala is critically involved in the affective coloring of sensory stimuli, the increase in T3 concentrations in the mitochondria of this brain region may be of relevance for the mechanism of action of anti-depressant drugs.

Extraction and quantification of thyroid hormones in selected regions and subcellular fractions of the rat brain

There is increasing evidence of an involvement of thyroid hormones in numerous physiological processes of the adult vertebrate brain. However, the only valid method available for measuring triiodothyronine (T3) in brain tissue is time-consuming and not sufficiently sensitive to determine hormone concentrations in small, but physiologically important areas such as the amygdala and septum. We therefore developed a protocol for reliable measurement of the concentrations of thyroxine (T4) and T3 in brain tissue. This was achieved by combining a new method of extracting iodothyronines with highly sensitive, accurate and reproducible radioimmunoassays (RIAs) in order to be able to detect T4 and T3 in homogenates and even subcellular fractions (nuclear, synaptosomal and mitochondrial) in up to 11 regions of the rat brain. The iodothyronines were extracted from tissue samples by adding 100% methanol containing 1 mM PTU. Recoveries of 72.8 +/- 5.5% and 83.2 +/- 3.3% for T4 and T3, respectively, were obtained. The RIA detection thresholds were 10 fmol/g for T4 and 18 fmol/g for T3. Only 0.2% of the antibody for T4 cross-reacted with T3 and 0.95% reverse T3. T3 antibody (0.05%) reacted with T4 and 0.01% with 3,5-T2. The T4 concentrations in the homogenates of selected areas of the brain ranged between 1 and 4 pmol/g, whereas those of T3 ranged between 0.5 and 4 pmol/g. The T3 levels ranged between 190 and 470 fmol/mg protein, 38 and 110 fmol/g protein and 25 and 180 fmol/mg protein in the nuclei, synaptosomes and mitochondriae, respectively. In conclusion, the newly developed method enabled us to determine both T4 and T3 concentrations in homogenates and T3 in subcellular fractions of regions of the brain as small as the septum and amygdala.

Gene expression of glucose transporters and glycolytic enzymes in the CNS of rats behaviorally dependent on ethanol

The steady-state levels of messenger RNA (mRNA) of the glucose transporters 1 and 3 and the glycolytic enzymes hexokinase, phosphofructokinase, glyceraldehyde-3-phosphate dehydrogenase and pyruvate dehydrogenase were measured in up to seven brain regions of the rat in a recently developed animal model of 'behavioral dependence' on ethanol. Irreversible behavioral dependence, including loss of control, was induced by offering the rats the choice between ethanol and water over a 9-month period (Group A). This group was compared with a group given the choice between ethanol and water for only 2 months (not yet behaviorally dependent, Group B), a group forced to consume ethanol as sole fluid over a 9-month period (not behaviorally dependent, Group C) and ethanol-naive control rats. All groups were sacrificed 1 month after ethanol withdrawal. The mRNA concentrations of both neuronal glucose transporter 3 and the key glycolytic enzymes phosphofructokinase and pyruvate dehydrogenase were significantly reduced in the hippocampi of the rats behaviorally dependent on ethanol (Group A). No significant changes were seen in any of the remaining brain regions (e.g., cortical areas, limbic forebrain, amygdala, midbrain) in Group A, or in any brain area at all in Groups B and C. The results show that chronic consumption of ethanol in a free-choice situation may impair neuronal glucose uptake and glycolytic flux. This effect is manifested exclusively in the hippocampus and is specifically related to the development of behavioral dependence, since it was not found after forced administration of large amounts of ethanol (Group C).

3,3'-Diiodothyronine concentrations in the sera of patients with nonthyroidal illnesses and brain tumors and of healthy subjects during acute stress

In this article we describe the development of a highly sensitive, accurate, and reproducible RIA for the measurement of 3,3'-diiodothyronine (3,3'-T2) in human serum and brain tissue. The detection limits were 1.8 fmol/g and 1.5 pmol/L in human brain tissue and serum, respectively. Serum concentrations of 3,3'-T2 were measured in 4 groups of patients with nonthyroidal illnesses (NTI), i.e. brain injuries (n = 15), sepsis (n = 24), liver disease (n = 22), and brain tumors (n = 23). The mean serum concentration of 3,3'-T2 in 62 healthy controls was 46.6 +/- 20.0 pmol/L. 3,3'-T2 levels declined significantly with increasing age. They were significantly lower in patients with brain injury (34.2 +/- 19.4 pmol/L; P = 0.006), were at the upper limit of normal in patients with sepsis (57.0 +/- 36.9 pmol/L; P = 0.06), and were elevated in patients with liver disease (72.6 +/- 56.7 pmol/L; P = 0.04) and brain tumors (89.0 +/- 40.9 pmol/L; P = 0.01). The serum levels of T3 were significantly lower than those in controls in all 4 patient groups. Serum concentrations of 3,3'-T2 were significantly enhanced in 9 patients with hyperthyroidism (85.4 +/- 43.0 pmol/L; P = 0.01) and were reduced in 12 patients with hypothyroidism (14.9 +/- 9.2 pmol/L; P = 0.001). In both normal brain tissue, obtained either intraoperatively or excised postmortem, and brain tumors, the concentrations of 3,3'-T2 ranged between 50-300 fmol/g. In healthy controls, 2 different forms of acute stress (sleep deprivation and delivering a lecture) significantly increased serum levels of T4 and T3, but did not affect those of 3,3'-T2 or 3,5-T2. In conclusion, our results show that, contrary to expectation, a low T3 syndrome in NTI is not always associated with low serum concentrations of 3,3'-T2. The production of 3,3'-T2 in NTI seems to be regulated in a disease-specific manner, resulting in unchanged, reduced, or elevated hormone concentrations.

Rat brain type II 5'-iodothyronine deiodinase activity is extremely sensitive to stress

The effects of different kinds of acute stressor on thyroid hormone concentrations and deiodinase activities were investigated in four brain regions (frontal cortex, amygdala, hypothalamus, and cerebellum) and in the pituitaries and livers of adult male rats. Five groups of rats were killed after each of the following stressors: (a) an intraperitoneal injection of saline, (b) intragastric intubation, (c) and (d) two different forms of handling, being grasped as for intraperitoneal injection and being moved from one cage to another, and (e) a 2-h period spent in a slowly rotating drum. Two other groups were placed in the rotating drums for 10 and 19 h (sleep deprivation experiment), respectively. All stressors induced significant (in some cases up to 200%) increases in the activity of type II 5'-iodothyronine deiodinase, which catalyzes the deiodination of the prohormone L-thyroxine (T4) to the active metabolite 3,3',5-triiodo-L-thyronine (T3). As a consequence, the tissue concentrations of T4 fell, and those of T3 rose (sometimes by up to 300%). However, these changes were limited to selected areas of the brain that were specific for each stressor and were not seen in all brain regions investigated in any group. No clear-cut effects of stress were seen on the activities of the type III 5-iodothyronine deiodinase isoenzyme, which catalyzes the inactivation of T3, on liver or serum thyroid hormone concentrations or on liver of brain type I 5'-iodothyronine deiodinase activities. In summary, our results show that even mild and very brief stress can induce marked increases in T3 concentrations specifically in brain but not in liver or blood. Thus, contrary to common opinion, thyroid hormones may play an important physiological role in stress reactions, at least in tissues that contain type II 5'-iodothyronine deiodinase, such as brain and pituitary.

Effects of acute administration of ethanol and the mu-opiate agonist etonitazene on thyroid hormone metabolism in rat brain

The effects of acute, low-dose administration of ethanol (1 g/kg bodyweight) and the mu-opioid receptor agonist etonitazene (30 microg/kg bodyweight) on the activities of the iodothyronine deiodinase isoenzymes were investigated in nine regions of the rat brain. The experiments were performed at three different times of the 24-h cycle (1300, 2100 and 0500 hours) and the rats were decapitated 30 and 120 min after administration of the respective drugs. Interest was focused on changes in the two enzymes that catalyze 1) 5'-deiodination of thyroxine (T4) to the biologically active triiodothyronine (T3), i.e. type II 5'-deiodinase (5'D-II) and 2) 5 (or inner-ring) deiodination of T3 to the biologically inactive 3'3-T2, i.e. type III deiodinase (5D-III). 120 min after administration of ethanol and etonitazene 5D-III activity was selectively inhibited in the frontal cortex (at 1300 and 1700 hours) and the amygdala (at all three measuring times). The 5'D-II activity was significantly enhanced 30 min after administration of etonitazene in the frontal cortex, amygdala and limbic forebrain, and after administration of ethanol in the amygdala alone. These effects on 5'D-II activity were seen at 2100 hours only. In conclusion, the two different addictive drugs both reduced the inactivation of the physiologically active thyroid hormone T3 and enhanced its production. These effects occurred almost exclusively in the brain regions which were most likely to be involved in the rewarding properties of addictive drugs. As thyroid hormones have stimulating and mood-elevating properties, an involvement of these hormones in the reinforcing effects of addictive drugs seems conceivable.

Dopamine receptor gene expression in an animal model of 'behavioral dependence' on ethanol

The steady-state levels of messenger RNA (mRNA) of five cloned dopamine (D) receptors were measured in five brain regions in rats in a recently developed animal model of 'behavioral dependence' on ethanol. One group of rats was given the choice between ethanol and water over a 9-month period and developed 'behavioral dependence' on ethanol (group a). This group was compared with a group given the choice between ethanol and water for only 2 months (not yet behaviorally dependent, group b), a group forced to consume ethanol as sole fluid over a 9-month period (not behaviorally dependent, group c) and ethanol-naive control rats. All groups were sacrificed 1 month after ethanol withdrawal. The concentrations of mRNA of D3-receptors in the limbic forebrain (which included the nucleus accumbens) were significantly lowered in groups a and b, but unchanged in group c. D3 mRNA levels were reduced in the hippocampus of group b and unchanged in the cortex, amygdala and striatum. No significant changes in the mRNA concentrations of D1-, D2-, D4- or D5-receptors were seen in the five brain regions in any group. In conclusion, chronic consumption of ethanol under the 'free-choice condition', which may best induce the drug-rewarding effect, leads to specific changes in the D3-receptor gene expression which were not seen after forced ethanol administration. Changes in D3 mRNA levels were, however, not a specific correlate of 'behavioral dependence', as they were also detected in rats not yet 'behaviorally dependent' (group b).

Thyroid hormone metabolism in the rat brain in an animal model of 'behavioral dependence' on ethanol

Thyroid hormone metabolism was investigated in the frontal cortex and amygdala in groups of rats either 'behaviorally dependent' on ethanol or chronically exposed to ethanol, but not 'dependent'. The activities of the 5'II deiodinase isoenzyme, which catalyzes the deiodination of thyroxine (T4) to the active metabolite triiodothyronine (T3), was elevated in the frontal cortex in both the 'behaviorally dependent' and the 'non-dependent' rats. The activities of the 5-II deiodinase isoenzyme, which catalyzes the inactivation of T3 to 3,3'-T2 was, however, selectively inhibited in the amygdalas of the rats 'behaviorally dependent' on ethanol, but normal in the 'non-dependent' rats. This suggests that increases in intracellular concentrations of T3 in the amygdala may be specifically related to reward mechanisms and the development of 'behavioral dependence' on ethanol.

Elevated 3,5-diiodothyronine concentrations in the sera of patients with nonthyroidal illnesses and brain tumors

This study reports the development of a highly sensitive and reproducible RIA for the measurement of 3,5-diiodothyronine (3,5-T2) in human serum and tissue. The RIA employs 3-bromo-5-[125I]iodo-L-thyronine (3-Br-5-[125I]T1) as tracer, which was synthesized carrier free by an interhalogen exchange from 3,5-dibromo-L-thyronine (3,5-Br2T0). The detection limits were 1.0 fmol/g and 0.8 pmol/L in human brain tissue and serum, respectively. T3, diiodothyroacetic acid, and 3-monoiodothyronine cross-reacted with a 3,5-T2 antibody to the extent of 0.06%, 0.13%, and 0.65%, respectively. Serum concentrations of 3,5-T2 were measured in 62 healthy controls and 4 groups of patients with nonthyroidal illness, i.e. patients with sepsis (n = 24), liver diseases (n = 23), head and/or brain injury n = 15), and brain tumors (n = 21). The mean serum level of 3,5-T2 in the healthy subjects was 16.2 +/- 6.4 pmol/L. Concentrations of 3,5-T2 were significantly elevated in patients with sepsis (46.7 +/- 48.8 pmol/L; P < 0.01), liver diseases (24.8 +/- 14.9 pmol/L; P < 0.01), head and/or brain injury (24.1 +/- 11.3 pmol/L; P < 0.05), and brain tumors (21.6 +/- 4.8 pmol/L; P < 0.01). In all 4 patient groups, serum levels of T3 were significantly reduced, confirming the existence of a low T3 syndrome in these diseases. Serum concentrations of 3,5-T2 were significantly elevated in patients with hyperthyroidism (n = 9) and were reduced in patients with hypothyroidism (n = 8). The levels of T4, T3, and 3,5-T2 were measured in normal human tissue samples from the pituitary gland and various brain regions and in brain tumors. In normal brain tissue, the concentrations of 3,5-T2 ranged between 70-150 fmol/g, and the ratio of T3 to 3,5-T2 was approximately 20:1. In brain tumors, however, T3 levels were markedly lower, resulting in a ratio of T3 to 3,5-T2 of approximately 1:1. Recent findings suggest a physiological, thyromimetic role of 3,5-T2, possibly stimulating mitochondrial respiratory chain activity. Should this prove to be correct, then the increased availability of 3,5-T2 in nonthyroidal illness may be one factor involved in maintaining clinical euthyroidism in patients with reduced serum levels of T3 during nonthyroidal illness.

Effects of lithium and carbamazepine on thyroid hormone metabolism in rat brain

The effects of lithium (LI) and carbamazepine (CBM) on thyroid hormone metabolism were investigated in 11 regions of the brain and three peripheral tissues in rats decapitated at three different times of day (4:00 A.M., 1:00 P.M., and 8:00 P.M.). Interest was focused on the changes in the two enzymes that catalyze: (1) the 5'deiodination of T4 to the biologically active T3, i.e., type II 5'deiodinase (5'D-II) and (2) the 5 (or inner-ring) deiodination of T3 to the biologically inactive 3'3-T2, i.e., type III 5 deiodinase (5D-III). A 14-day treatment with both LI and CBM induced significant reductions in 5D-III activity. However, 5'D-II activity was elevated by CBM and reduced by LI, both administered in concentrations leading to serum levels comparable with those seen in the prophylactic treatment of affective disorders. The effects were dose dependent, varied according to the region of the brain under investigation, and strongly depended on the time of death within the 24-hour rhythm. The consequences of these complex effects of LI and CBM on deiodinase activities for thyroid hormone function in the CNS and also their possible involvement in the mechanisms underlying the mood-stabilizing effects of both LI and CBM remain to be investigated.

Phenolic and tyrosyl ring iodothyronine deiodination and thyroid hormone concentrations in the human central nervous system

In the present study we investigated the biochemical properties of in vitro phenolic (5'D) and tyrosyl (5D) ring deiodination and the tissue concentrations of T4, T3, and rT3 in adult human central nervous system (CNS) tissue. All samples were obtained from nontumoral tissue at autopsy (n = 6) or neurosurgical operation (n = 5). Both phenolic and tyrosyl ring deiodinase activities were demonstrable in all samples obtained intraoperatively, whereas only tyrosyl ring deiodination was evident in the tissues obtained postmortem. The phenolic ring deiodination pathway corresponded to the type II 5'-deiodinase isoenzyme with regard to its high affinity for T4 and rT3 (Km = 2.2 and 2.4 nmol/L, respectively), its insensitivity to 6-propyl-n-2-thiouracil (PTU), and the sequential reaction mechanism. No PTU-sensitive 5'-deiodination of rT3 was demonstrable. Tyrosyl ring deiodination of both T4 and T3 showed typical type III 5D kinetics (Ka, 6.5 nmol/L for T4 and 3.4 nmol/L for T3) and was PTU insensitive. Nanomolar concentrations of tissue T4, T3, and rT3 were detected in samples obtained both intraoperatively and postmortem. They were very similar to the absolute values of the apparent Km for T4, T3, and rT3 in the phenolic and tyrosyl ring deiodination pathways. In conclusion, we have demonstrated the coexistence of both phenolic and tyrosyl ring deiodinase activities in the human CNS. Their kinetic characteristics, substrate specificity, and reaction mechanisms are very similar to the corresponding type II 5'- and type III 5-iodothyronine deiodinase activities in rat brain. In contrast to the findings in the rat CNS, no PTU-sensitive phenolic ring deiodinase (i.e. type I 5'D) activity was found in the human CNS. This may explain the relatively high tissue concentrations of rT3.