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Biomedical subjects

J Köhrle

Publications and source records attributed to J Köhrle.

At least 19 recordsLinked to original sources
PubMed2006

Proenkephalin A 119-159, a stable proenkephalin A precursor fragment identified in human circulation.

In this report, we describe a newly developed sandwich immunoassay using antibodies against the proenkephalin A 119-159 peptide (PENK A 119-159). PENK A 119-159 immunoreactivity was detectable in the circulation of human blood donors and in cerebrospinal fluid (CSF) of patients without a neurologic disorder. The concentration was about 100 times higher in CSF than in serum. Analytical reversed phase HPLC revealed that PENK A 119-159 is the main immunoreactivity in human circulation and CSF. Moreover, PENK A 119-159 is stable in vitro for at least 48 h at room temperature as compared to the low stability of the peptides methionine- and leucine-enkephalin. This suggests the use of PENK A 119-159 measurement as surrogate molecule for the release of the mature peptides derived from proenkephalin A.

Amino Acid Sequence↗
PubMed2005

Selenium, the thyroid, and the endocrine system.

Recent identification of new selenocysteine-containing proteins has revealed relationships between the two trace elements selenium (Se) and iodine and the hormone network. Several selenoproteins participate in the protection of thyrocytes from damage by H(2)O(2) produced for thyroid hormone biosynthesis. Iodothyronine deiodinases are selenoproteins contributing to systemic or local thyroid hormone homeostasis. The Se content in endocrine tissues (thyroid, adrenals, pituitary, testes, ovary) is higher than in many other organs. Nutritional Se depletion results in retention, whereas Se repletion is followed by a rapid accumulation of Se in endocrine tissues, reproductive organs, and the brain. Selenoproteins such as thioredoxin reductases constitute the link between the Se metabolism and the regulation of transcription by redox sensitive ligand-modulated nuclear hormone receptors. Hormones and growth factors regulate the expression of selenoproteins and, conversely, Se supply modulates hormone actions. Selenoproteins are involved in bone metabolism as well as functions of the endocrine pancreas and adrenal glands. Furthermore, spermatogenesis depends on adequate Se supply, whereas Se excess may impair ovarian function. Comparative analysis of the genomes of several life forms reveals that higher mammals contain a limited number of identical genes encoding newly detected selenocysteine-containing proteins.

Animals↗
PubMed2004

Selenium and selenoproteins in mammals: extraordinary, essential, enigmatic.

Selenium (Se), once known only for its potential toxicity, is now well established as an essential trace element for mammals. Insufficient Se intake predisposes to and manifests in a variety of diseases. Recent studies have proven that it is the synthesis of selenocysteine (Sec)-containing proteins, designated selenoproteins, which represents an essential prerequisite for regular development and a long and healthy life. New transgenic mouse models analysing those selenoproteins with proven enzymatic functions displayed particular phenotypes and highlighted essential Se-dependent processes in development, growth or against specific challenges. While there is a growing molecular understanding of and general agreement on the importance of sufficiently high Se intake and undisturbed selenoprotein biosynthesis, many of the recently identified selenoproteins are still uncharacterised, and the effects and consequences of supra-physiological Se dosages are not biochemically understood. With the recent definition of the human and mouse selenoproteomes and a growing number of available tools, the Se field is now geared for a great leap forward. Se biology has already broadened our knowledge about the genetic code and about protein translation. It now holds great promises also for a better understanding of some key aspects of cancer, inflammation, fertility and prevention of age-associated diseases.

Animals↗
PubMed2004

Contribution of interleukin-12 to the pathogenesis of non-thyroidal illness.

Changes in both central and peripheral thyroid hormone (TH) metabolism occur during illness. These changes, known collectively as non-thyroidal illness, are apparently mediated by the proinflammatory cytokines IL-6, TNFalpha and IFNgamma. IL-12 is involved in regulation of IFNgamma and TNFalpha. The aim of this study was to evaluate the role of IL-12 in TH metabolism during illness. We studied TH metabolism both centrally (in the pituitary) and peripherally (in the liver) in IL-12 knock-out (IL-12 (-/-)) and wild type (WT) mice during illness induced by administration of bacterial endotoxin (LPS). LPS induced a similar decrease in serum T (3), T (4) and liver 5'-DI mRNA expression in IL-12 (-/-) and WT mice with the exception of a smaller reduction of serum T (4) in IL-12 (-/-) mice. In the pituitary, the LPS-induced decline in 5'-DI activity in WT mice was not observed in IL-12 (-/-) mice (p < 0.001), whereas the decrease in DII activity tended to be smaller in IL-12 (-/-) mice (p = 0.066). The lower decrease in pituitary activity of both DI and DII in IL-12 (-/-) mice is possibly related to the lower LPS-induced T (4) decrease. In conclusion, IL-12 is involved in the central regulation of the HPT axis during illness but not in the peripheral regulation.

Animals↗
PubMed2002

The promoter of the human sodium/iodide-symporter gene responds to retinoic acid.

It was shown previously that hNIS mRNA expression is stimulated by retinoic acid (RA) in human follicular thyroid carcinoma cell lines FTC-133 and FTC-238, and patients with thyroid carcinomas lacking iodide uptake respond to RA treatment with increased radioiodide transport. Here, in transient transfection experiments using FTC-238 cells, hNIS promoter/luciferase reporter constructs showed an up to 2.5-fold increase in transcriptional activity after incubation with 1 microM RA. Stimulation by 10 nM T3 was up to 2.4-fold. Deletion or block mutation of a putative nuclear receptor recognition site, 'DR10', abolished RA and T3 responses. Four copies of the DR10 cloned 5' to the thymidine kinase promoter gave a 2.6-fold and a 1.4-fold increase in transcriptional activity after RA and T3 stimulation, respectively. In electrophoretic mobility shifts, a wildtype DR10 oligonucleotide, but not block mutants of either DR10 halfsite, interacted with nuclear receptors. Thus, RA redifferentiation of advanced thyroid carcinomas may reinduce iodide uptake by stimulating hNIS expression and thereby make tumours accessible for radioiodide therapy again.

Adenocarcinoma, Follicular↗
PubMed2002

Clinical impact of retinoids in redifferentiation therapy of advanced thyroid cancer: final results of a pilot study.

Differentiated thyroid cancer is a malignant tumour that has a fairly good prognosis, with patients surviving for many years. Multimodal therapy with surgery, radioiodine therapy and TSH suppressive medication is of proven efficacy. However, loss of differentiation is observed in up to one-third of patients with differentiated thyroid cancer, paralleled by an increase in tumour grading and loss of thyroid-specific functions (thyrotropin receptor, iodine accumulation). Such tumours may no longer be amenable to standard treatment protocols, including TSH suppression and radioiodide therapy. Retinoic acids have been shown to exert re-differentiating effects on thyrocytes in various experimental studies and case reports, and it was on this basis that this pilot study was initiated. Patients with advanced thyroid cancer and without the therapeutic options of operation or radioiodide therapy were treated with 13- cis-retinoic acid at a dosage of 1.5 mg/kg body weight daily over 5 weeks. Parameters for assessment of the therapeutic effect were serum thyroglobulin (TG) levels, radioiodine uptake, and tumour size prior to and after retinoid treatment. Fifty patients were evaluated for response, classified as reduction in tumour size and TG levels, stable disease or disease progression. Thirteen patients showed a clear increase in radioiodine uptake, and eight a mild increase. TG levels were unchanged or decreased in 20 patients. Tumour size was assessable in 37 patients; tumour regression was observed in six, and there was no change in 22. In total, a response was seen in 19 patients (38%). Response to retinoid therapy did not always correlate with increased radioiodine uptake, so other direct antiproliferative effects have to be assumed. The encouraging results of the study and the low rate of side-effects with good tolerability of retinoids warrant further studies with altered inclusion criteria and employment of other redifferentiating drugs or combinations of agents.

Adenocarcinoma↗
PubMed2002

Thyroid hormone receptors and type I iodothyronine 5'-deiodinase activity of human thyroid toxic adenomas and benign cold nodules.

The majority of thyroid adenomas are of clonal origin. In a subset of toxic adenomas (TAs) and cold nodules (CNs) activating mutations in the thyrotropin (TSH) receptor or G s -alpha gene may explain the altered functions in these benign tumours. The present study was undertaken to investigate the status of functional thyroid hormone receptors, major thyroid hormone signal mediators, in both the human TAs and CNs in comparison with a normal thyroid tissue from the same patient. Electrophoretic mobility shift assays using a DR4 ("direct repeats" 4), a thyroid hormone responsive element (TRE) of human type I iodothyronine 5'-deiodinase demonstrated the DNA-binding of thyroid hormone receptors (TRs) in thyroid tissue nuclear extracts. A significant increase (p < 0.05) in the functional binding properties of TRs to the DR4 thyroid hormone responsive element was found in TAs when compared to normal thyroid tissue. Contrary, a marked diminution in the TR-TRE complex formation was found in CNs in comparison with normal thyroid tissue. In addition, functional activity of the iodothyronine 5'-deiodinase (5'DI) was analyzed in benign tumours, thyroid TAs and CNs in comparison with that of normal thyroid tissue. A significantly increased (p < 0.01) activity of 5'DI was demonstrated in TAs, and in contrast, decreased values of the enzyme activity were found in CNs when compared to a normal tissue. From the data it is suggested that both the status of TR-TRE complex formation and the activity of the 5'DI may be altered in benign tumours of human thyroid gland.

Adenoma↗
PubMed2002

Expression of 5'-deiodinase enzymes in normal pituitaries and in various human pituitary adenomas.

OBJECTIVE: Local 5'-deiodination of l-thyroxine (T(4)) to active thyroid hormone 3,3',5-tri-iodothyronine (T(3)) catalyzed by the two 5'-deiodinase enzymes (D1 and D2) regulates various T(3)-dependent functions in the anterior pituitary and has been well studied in rodents. Only limited information about deiodinase expression and its cellular distribution in human anterior pituitaries is available. DESIGN: We examined 5'-deiodinase enzyme activities in pituitary adenomas (18 non-functioning, seven TSH-producing, one GH- and TSH-producing, five GH-producing, eight prolactin (PRL)-producing, two adenomas each from patients with Cushing's disease and Nelson's syndrome) and three normal anterior pituitaries. METHODS: Activities were measured as release of (125)I(-) from tyrosyl-ring labeled reverse T(3) with or without propylthiouracil, a potent inhibitor of D1 which does not influence D2 activities. RESULTS: Most of the adenomas and normal tissues expressed both isoenzymes, with D2 activity higher than D1. In a few tissues D1 activity was higher than D2 and some tissues did not express D1 activity at all. Highest activities of both enzymes were found in TSH- and PRL-producing adenomas but absolute activities and the D1/D2 ratio were variable in the same kind of tumor in different patients. CONCLUSION: The finding that all examined tissues expressed 5'-deiodinase activity, most of them expressing both isoenzymes, implies that both enzymes are still active in tumors and that local deiodination is important for the function and feedback regulation of human anterior pituitary.

Adenoma↗
PubMed2001

Modulation of selenoprotein P expression by TGF-beta(1) is mediated by Smad proteins.

Selenoprotein P (SeP) is a selenium-rich plasma protein which accounts for more than 50% this study, the effect of TGF-beta(1) on the expression of SeP in the human liver cell line HepG2 was investigated. Western analysis revealed a dose-dependent reduction of SeP content in cell supernatant. RT-PCR analysis of SeP-mRNA expression demonstrated a marked inhibition and a reporter gene under control of the SeP promoter was negatively regulated by TGF-beta(1). Smad proteins are the transcriptional mediators of TGF-beta signaling. A putative Smad-binding element (SBE) is present in the SeP promoter. In electrophoretic-mobility-shift assays, TGF-beta(1) enhanced the binding of nuclear proteins to this SBE. Overexpression of Smad3 and 4 resulted in a downregulation of SeP-promoter activity whereas deletion of the SBE led to a loss of TGF-beta(1) responsiveness. We conclude that SeP expression is modulated by the binding of Smad3/4 complexes to a functional SBE in the SeP promoter.

Base Sequence↗
PubMed2001

Identification of an element within the promoter of human selenoprotein P responsive to transforming growth factor-beta.

Selenoprotein P (SeP) is a plasma protein that contains up to 10 selenocysteine residues and accounts for about 50% of total selenium in human plasma. We have previously shown that SeP expression in the human liver cell line HepG2 is inhibited by transforming growth factor (TGF)-beta1 on a transcriptional level. Smad proteins are the transcriptional mediators of TGF-beta signalling and putative Smad-binding elements (SBE) comprising the core sequence CAGACA are present at two positions in the SeP promoter. The aim of our study was to investigate whether Smad molecules are involved in inhibition of SeP expression by TGF-beta1 and to locate the promoter region critical for this effect. As seen in electrophoretic-mobility-shift assays, TGF-beta1 treatment led to enhanced binding of nuclear proteins to a putative SBE from the SeP promoter. Overexpression of Smad 3 and 4, but not of Smad 2, resulted in a marked down-regulation of SeP mRNA expression. Similar effects were observed for luciferase expression under control of a human SeP-promoter construct. Deletion as well as point-mutation of putative SBEs led to a loss of promoter sensitivity towards TGF-beta1 treatment. Hence, we demonstrated an involvement of Smad 3 and 4 in transcriptional regulation of SeP by TGF-beta1 and we were able to identify the TGF-beta-responsive element in the SeP promoter.

Base Sequence↗
PubMed2000

The influence of the cytokines Il-1beta and INFgamma on the expression of selenoproteins in the human hepatocarcinoma cell line HepG2.

Metabolic labeling of HepG2 cells with 75selenite indicated the expression of more than four selenoproteins in the 80 to 45 kDa range and more than four selenoproteins in the 24 to 14 kDa range. Although there were no significant changes in the total protein content, determined by the method of BioRad, the densitometric analysis of the autoradiogramms showed a reduced expression of all labeled selenoproteins in the cell lysates of HepG2 after cytokine treatment for 24 hours. A stronger reduction was observed after treatment with Il-1beta than with IFNgamma. Moreover, the inhibitory effects were more significant for those selenoproteins in the higher molecular mass range. Our data on the inhibition of selenoprotein synthesis and on repression of SeP promoter activity show that the expression of selenoproteins, especially of SeP, is influenced by acute phase reaction and pro-inflammatory reactions.

Gene Expression↗
PubMed2000

The deiodinase family: selenoenzymes regulating thyroid hormone availability and action.

Thyroid hormones control growth, development, differentiation and metabolism in vertebrates. Most of the actions of the active thyroid hormone T3 (3,5,3'-triiodo-L-thyronine) are exerted via ligand-activated nuclear T3 receptors. Activation of the secretory product of the thyroid gland, L-thyroxine (3,3',5,5'-tetraiodo-L-thyronine), or T4, is catalyzed by two enzymes, iodothyronine-5'-deiodinases type I and type II. Inactivation of T4 and T3 occurs via type III iodothyronine-5-deiodinase and to some extent by type I 5'deiodinase. Complementary DNAs (cDNAs) encoding the substrate-binding selenocysteine-containing subunits of the deiodinases were cloned, though some controversy still exists on the type II 5'-deiodinase subunits. Characterization of tissue-specific expression patterns indicates that these selenium-dependent enzymes exert tight control on local and systemic availability of active T3. Thus, deiodinases are envisaged as guardians to the gate of thyroid hormone action mediated by T3 receptors.

Animals↗
PubMed2000

Thyroid hormone metabolism and action in the brain and pituitary.

Brain and pituitary development, maturation, and function critically depend on thyroid hormone availability. The identification of several forms of nuclear T3-receptors, the region-specific expression of deiodinase isoenzymes in brain and pituitary, and the molecular analysis of thyroid hormone-responsive genes in fetal, newborn, and adult brain opened a new era in the understanding of thyroid hormone action. These integrated networks of receptors, deiodinases, and thyroid hormone responsive genes require strict regulation of thyroid hormone concentration at the right place and the appropriate time. Knockout and transgenic mouse models of components involved in hypothalamus-pituitary-thyroid-periphery-feedback regulation revealed that lack of thyroid hormone (such as during iodine deficiency) leads to defects and phenotypes other than lack of thyroid receptor(s). In many aspects, expression of mutant thyroid receptors is worse than lack of wild-type receptors. Thyroid hormones control several genes in the CNS and are also essential for differentiation of pituitary lactotrophs and somatotrophs. Apart from most T3 effects which are mediated by nuclear receptors, T4 itself as well as its lower iodinated metabolites exert direct biological effects in the brain by mechanisms not involving nuclear T3-receptors.

Animals↗
PubMed2000

Retinoic acid redifferentiation therapy for thyroid cancer.

For the treatment of differentiated thyroid cancer, surgery, radioiodide therapy, and thyrotropin-suppressive thyroxine application represent established therapeutic measures of proven efficiency, affording a good prognosis for this disease. However, in up to 30% of the cases, dedifferentiation is observed, giving rise to tumors that are refractory to conventional treatment. Eventually, this may lead to the most malignant human tumor, anaplastic thyroid carcinoma, with a life expectancy of only a few months after diagnosis. Among novel approaches for the treatment of dedifferentiated thyroid carcinomas, retinoic acid redifferentiation therapy was evaluated in several in vitro and in vivo studies. Cell culture experiments in thyroid carcinoma lines show that RA treatment affects thyroid specific functions (type I 5'-deiodinase, sodium/iodide-symporter), cell-cell or cell-matrix interaction (intercellular adhesion molecule-1, E-cadherin), differentiation markers (alkaline phosphatase, CD97), growth, and tumorigenicity. The observed changes, which involve multiple parameters that characterize a mature, functional thyrocyte, may be interpreted as partial redifferentiation. In clinical pilot studies, about 40% of the patients responded to RA application with an increased radioiodide uptake. In an evaluation of 20 RA-treated patients with well-documented data sets, 8 exhibited a decrease (4) or stabilization (4) in tumor size and/or in serum thyroglobulin levels in addition to enhanced radioiodide transport. This indicates that these patients with a long history of unresponsiveness to other treatment may have experienced an actual therapeutic benefit. These data suggest that RA redifferentiation therapy, considering especially its comparatively mild side effects, may soon represent an alternative therapeutic approach to otherwise untreatable thyroid tumors.

Cell Line↗
PubMed2000

Inverse mRNA expression of the selenocysteine-containing proteins GI-GPx and SeP in colorectal adenomas compared with adjacent normal mucosa.

Four selenocysteine-containing proteins (gastrointestinal glutathione peroxidase, plasma glutathione peroxidase, selenoprotein P, and thioredoxin reductase-alpha) are expressed in the colonic mucosa. Because of their antioxidant functions, a protective role in colon carcinogenesis is discussed. The aim of this study was to elucidate an involvement of gastrointestinal selenoproteins during the adenoma-carcinoma sequence. Matched pairs of biopsies of colorectal adenomas and adjacent normal mucosa from 11 patients were analyzed for mRNA expression, protein expression, or enzyme activity of selenoproteins by Northern blot, Western blot, or enzymatic tests. All adenomas revealed a marked reduction of selenoprotein P and a variable increase of gastrointestinal glutathione peroxidase mRNA compared with adjacent tissue. Thioredoxin reductase-alpha and plasma glutathione peroxidase mRNA expression were not altered in adenomas. The Northern blot results were confirmed by Western blot analysis or enzyme activity measurement, respectively. We conclude that gastrointestinal glutathione peroxidase and selenoprotein P play a complementary role in the antioxidative cell defense along the adenoma-carcinoma sequence. It remains to be shown whether upregulation of gastrointestinal glutathione peroxidase in adenomas represents a compensatory mechanism to reduce susceptibility for oxidative damage resulting from the loss of selenoprotein P.

Adenoma↗
PubMed2000

Effects of proinflammatory cytokines on anterior pituitary 5'-deiodinase type I and type II.

Cytokines are locally produced in the anterior pituitary and act through para-/autocrine mechanisms to modulate cell growth and hormone production. 5'-Deiodinases type I (D1) and type II (D2) are also expressed in the anterior pituitary and play an integrative role in the regulation of hormone production and pituitary feedback. D1 activity is known to be regulated by proinflammatory cytokines in liver and thyroid. Therefore, we examined the effects of IL-1 beta, IL-6 and TNF alpha on 5'-deiodinase activities in reaggregates of rat anterior pituitaries and rat somatomammotroph GH3 cells cultured alone, or in a bicameral culture system together with the murine folliculo-stellate (FS) cell line TtT/Gf. In reaggregate cultures of rat anterior pituitaries IL-1 beta stimulated D1 and D2 dose-dependently and D2 activity was increased by TNF alpha. When GH3 cells were cocultured with TtT/Gf cells, D2 activities were 2.3-fold lower than in GH3 cells cultured alone. TNF alpha (50 ng/ml) and IL-6 (100 U/ml) stimulated D2 in GH3 cells when the cells were cultured alone and treated with these cytokines for 24 h. When TtT/Gf cells in the coculture model were treated with IL-1 beta, TNF alpha and IL-6, no effect on D1 or D2 activities in GH3 cells was observed. In male, adult rats a single LPS injection (i.p.) stimulated D2 and D1 activities in the anterior pituitary, and decreased liver D1 activities and serum TSH levels. In vitro, LPS stimulation of the coculture model of GH3 and FS cells also increased D1 activity. Electrophoretic mobility shift assays (EMSAs) revealed that IL-1 beta and TNF alpha activate the transcription factor NF kappa B in reaggregates of rat anterior pituitaries and in TtT/Gf cells cultured alone or cocultured with GH3 cells. Taken together, these findings imply that in anterior pituitary cells 5'-deiodinase activities are stimulated by locally produced cytokines in a para-/autocrine manner but cell types other than FS cells seem to mediate some of the effects.

Animals↗
PubMed1999

[Expression of selenoproteins in monocytes and macrophages--implications for the immune system].

Monocytes differentiate from myeloid precursors towards the macrophage state of differentiation under the influence of 1,25-dihydroxy vitamins D3 (1,25 [OH]2 vitamin D3) and other factors and this is further propagated by colony stimulating factors (MCSF and GMCSF). Macrophage activation and phagocytosis of foreign particles are regularly accompanied by a so called "respiratory burst", an increase in the production of reactive oxygen species (ROS), exerted by the enzyme complex NADPH oxidase. A number of antioxidant enzymes is expressed at the same time to protect the cells from the cytotoxic effects of ROS directed against engulfed microorganisms. The selenium-dependent glutathione peroxidases and thioredoxin reductases are important examples. The cytosolic GPx isoenzyme (cGPx) and thioredoxin reductase alpha (TrxR alpha) are upregulated during the process of differentiation and under the influence of 1.25 (OH)2 vitamin D3. GPx isoenzymes neutralize H2O2. TrxR reduce sulfhydryl-groups like in cysteins either directly or via their cofactor thioredoxin and thus are involved in protein folding and critical protein-protein and protein-DNA interactions, e.g. modulation of dimerization and/or DNA-binding and ligand binding of transcription factors (glucocorticoid receptor and other steroid receptors, NF kappa B). In addition, the antibiotic peptide NK-lysin was shown to be a substrate for TrxR alpha, suggesting that TrxR protects the cell itself from the cytotoxic effects of NK-lysin. Selenium is incorporated into selenocysteine (Secys) in a regulated fashion in the presence of a hairpin structure (Secis element) in the 3'UTR of selenoprotein genes. Secis elements direct the insertion of Secys at UGA codons, which function as opal stop codons in the absence of a suitable Secis element and in selenium deficiency. The above mentioned processes might therefore be altered in relative selenium deficiency or vice versa be upregulated through selenium supplementation. We have shown that TrxR alpha is a 1.25 (OH)2 vitamin D3-responsive early gene in monocytic cells and that TrxR activity as well as GPx activity in these cells can be upregulated by the addition of selenium in vitro and ex vivo. Recent work demonstrates that thioredoxin rapidly enters the cell nucleus upon treatment of cells with H2O2, but little is known about the compartimentalization of the respiratory burst and the intracellular localization of antioxidant enzymes during that process. Macrophage function is insufficient if the generation of a respiratory burst is altered like in hereditary chronic granulomatous disease on one hand, but on the other hand is as well disturbed, if there is a lack in antioxidant enzyme activity. Thioredoxin has been identified as a lymphocyte growth factor and might therefore be involved in the crosstalk between macrophages and lymphocytes. The relevance of the above mentioned and other yet undefined monocytic selenoproteins remains to be elucidated in detail as well as the relevance of selenium supplementation in nutrition in general and in situations of critical infectious disease and autoimmunity.

Animals↗