Selenium supplementation attenuates procollagen-1 and interleukin-8 production in fat-loaded human C3A hepatoblastoma cells treated with TGFbeta1.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) is associated with obesity, insulin resistance and hepatic steatosis. Non-alcoholic steatohepatitis (NASH) is a serious consequence of NAFLD where chronic tissue damage and inflammation result in fibrosis which may progress to cirrhosis. Transforming growth factor beta1 (TGFbeta1), proinflammatory cytokines and oxidative stress are thought to play crucial roles in the pathogenesis of these conditions. The contributions of individual liver cell types to fibrogenesis remain controversial and the influence of selenium status has not been investigated. METHODS: In this study we have used a cell culture model of fat-loading using oleate-treated human hepatoblastoma (C3A) cells to investigate how fat-loading and selenium status might influence the production of collagen in response to TGFbeta1. The secretion of inflammatory cytokines was also investigated, together with the epithelial character of the treated cells. RESULTS: We found that in response to treatment with TGFbeta1, C3A cells produced mRNA encoding the pro-alphaI chain of procollagen I, secreted procollagen I peptide, up-regulated production of the proinflammatory cytokine interleukin-8 (IL-8) and the mesenchymal marker vimentin, and down-regulated albumin production. Most of these responses were considerably enhanced when cells were fat-loaded with oleate and were attenuated by selenium addition at a dose that optimised the expression of thioredoxin reductase and glutathione peroxidase. CONCLUSIONS: Our data establish that both fat-loading and suboptimal selenium status enhance collagen and IL-8 production by C3A hepatocytes in response to TGFbeta1, possibly as part of an epithelial to mesenchymal transition. GENERAL SIGNIFICANCE: These findings suggest that the hepatocyte may be an important contributor to the pathogenesis of fibrosis associated with NAFLD.

Modulation of thioredoxin reductase-2 expression in EAhy926 cells: implications for endothelial selenoprotein hierarchy.

BACKGROUND: We examined the expression of the mitochondrial selenoenzyme TrxR2 in the endothelial cell line EAhy926 under conditions known to modify its cytoplasmic counterpart TrxR1. METHODS: Cells were cultured with varying concentrations of selenite, sulforaphane or the Ca2+ ionophore A23187 for 72-h, prior to assay of TrxR concentration and activity. Further cultures underwent prolonged (7-day) Se-depletion before selenoprotein measurement. RESULTS: In Se-deficient cultures, neither Se, A23187 or sulforaphane affected TrxR2 concentration, while these treatments induced TrxR1 concentration (p<0.05). When co-incubated, optimal concentrations of Se (40 nM) and sulforaphane (4 microM) only modestly increased TrxR2 protein (approximately 1.3-fold), compared with TrxR1 (approximately 4-fold). In Se-deficient cells, TrxR activity was unaffected by sulforaphane or A23187. Prolonged Se-depletion caused a comparatively small reduction in TrxR2 (66% TrxR2 retained) against TrxR1 and glutathione peroxidase-1 activity (38% and 17% retained, respectively). CONCLUSIONS: The relative resistance of TrxR2 to Se-deprivation and induction by sulforaphane and A23187 suggests TrxR2 lies near the top of the selenoprotein hierarchy in EAhy926 cells and exhibits near maximum expression under a range of culture conditions. In Se deficiency an inactive (possibly truncated) TrxR1 is produced in response to stimulus by sulforaphane and A23187. GENERAL SIGNIFICANCE: These observations underpin a likely critical antioxidant role for TrxR2 and TrxR1 in the endothelium.

Randomized controlled trial of the effect of selenium supplementation on thyroid function in the elderly in the United Kingdom.

BACKGROUND: Thyroid function depends on the essential trace mineral selenium, which is at the active center of the iodothyronine deiodinase enzymes that catalyze the conversion of the prohormone thyroxine (T(4)) to the active form of thyroid hormone, triiodothyronine (T(3)). OBJECTIVE: Because selenium intake in the United Kingdom has fallen during the past 25 y, we wanted to determine whether current selenium status might be limiting conversion of T(4) to T(3) in the elderly, in whom marginal hypothyroidism is relatively common. DESIGN: We investigated the effect of selenium supplementation in a double-blind, placebo-controlled trial in 501 elderly UK volunteers. Similar numbers of men and women from each of 3 age groups, 60-64 y, 65-69 y, and 70-74 y, were randomly allocated to receive 100, 200, or 300 microg Se/d as high-selenium yeast or placebo yeast for 6 mo. As part of the study, plasma selenium, thyroid-stimulating hormone, and total and free T(3) and T(4) were measured. Data from 368 euthyroid volunteers who provided blood samples at baseline and 6 mo were analyzed. RESULTS: Although selenium status at baseline correlated weakly with free T(4) (r = -0.19, P < 0.001) and with the ratio of free T(3) to free T(4) (r = 0.12, P = 0.02), we found no evidence of any effect of selenium supplementation on thyroid function, despite significant increases in plasma selenium. However, baseline plasma selenium in our study (x: 91 microg/L) was somewhat higher than in previous supplementation studies in which apparently beneficial effects were seen. CONCLUSION: We found no indication for increasing selenium intake to benefit T(4) to T(3) conversion in the elderly UK population.

Genetic polymorphisms in the human selenoprotein P gene determine the response of selenoprotein markers to selenium supplementation in a gender-specific manner (the SELGEN study).

Selenium (Se), a micronutrient essential for human health, is incorporated into at least 25 selenoproteins including selenoprotein P (SePP), which transports Se within the body. This research identified two single nucleotide polymorphisms (SNPs) in the SePP gene, one in the coding region (position 24731, causing an Ala to Thr change) and one in the 3'untranslated region (position 25191). Their frequency was similar in Caucasian, Chinese, and South Asian populations. Prospectively genotyped volunteers were supplemented for 6 wk with 100 microg sodium selenite/day. Blood samples were analyzed for plasma Se and selenoprotein biomarkers at baseline, after supplementation, and during a washout period. Plasma Se, SePP, and glutathione peroxidase 3 (GPx3) levels increased with supplementation. Baseline plasma Se content depended on both SePP genotypes and body mass index. Presupplementation SePP concentration was associated with gender and genotype at SNP 24731 and postsupplementation concentration with SNP 25191. Both SNPs and gender were associated with differences in GPx3 activity, plasma, and erythrocyte thioredoxin reductase 1 concentrations and lymphocyte glutathione peroxidase 1 and 4 activities and concentrations. In conclusion, the data reveal two common functional SNPs within the human SePP gene that may predict behavior of biomarkers of Se status and response to supplementation and thus susceptibility to disease.

Synergy between broccoli sprout extract and selenium in the upregulation of thioredoxin reductase in human hepatocytes.

Dietary isothiocyanates and selenium (Se) can up-regulate thioredoxin reductase 1 (TR1) in cultured human HepG2 and MCF-7 cells [Zhang et al. (2003). Synergy between sulforaphane and selenium in the induction of thioredoxin reductase 1 requires both transcriptional and translational modulation. Carcinogenesis, 24, 497-503; Wang et al. (2005). Sulforaphane, erucin and iberin up-regulate thioredoxin reductase expression in human MCF-7 cells. Journal of Agricultural and Food Chemistry, 53, 1417-1421] at both the protein and mRNA levels. In this study, broccoli sprout extract (a rich source of the isothiocyanates sulforaphane and iberin) and Se interacted synergistically to induce TR1 in immortalised human hepatocytes. Broccoli sprout extracts containing 1.6, 4 and 8µM isothiocyanates were tested for their ability to induce TR1 at the protein and mRNA level. Although induction of TR1 mRNA by broccoli sprout extract (1.6-8µM) was only 1.7-2.2-fold, co-treatment with Se (0.2-1µM) enhanced the expression of TR1 mRNA (3.0-3.3-fold). Moreover, broccoli sprout extract induced the cellular concentration of TR1 and TR enzymatic activity, an induction that was augmented by Se addition. Thus, broccoli sprout extract (8µM) and Se induced cellular TR1 concentration and enzymatic activity 3.7- and 5-fold respectively, whereas, Se or broccoli sprout extract alone produced an induction of only approximately 2-fold. These data suggest that dietary isothiocyanates from broccoli sprouts and Se are important agents in the regulation of redox status in human liver cells. The synergistic effect between isothiocyanates and Se at physiologically-relevant concentrations on the induction of TR1 may play an important role in protection against oxidative stress.

Dual action of sulforaphane in the regulation of thioredoxin reductase and thioredoxin in human HepG2 and Caco-2 cells.

We have previously demonstrated that sulforaphane is a potent inducer for thioredoxin reductase in HepG2 and MCF-7 cells (Zhang et al. Carcinogenesis 2003, 24, 497-503; Wang et al. J. Agric. Food Chem. 2005, 53, 1417-1421). In this study, we have shown that sulforaphane is not only an inducer for thioredoxin reductase but also an inducer for its substrate, thioredoxin in HepG2, and undifferentiated Caco-2 cells. Sulforaphane acts at two levels in the regulation of thioredoxin reductase/thioredoxin system by the upregulation of the expression of both the enzyme and the substrate. In human hepatoma HepG2 cells, sulforaphane induced thioredoxin reductase mRNA and protein by 4- and 2-fold, respectively, whereas thioredoxin mRNA was induced 2.9-fold and thioredoxin protein was unchanged in whole cell extracts, but an increase in nuclear accumulation (1.8-fold) was observed. Moreover, the induction of thioredoxin reductase was found faster than that of thioredoxin. The effects of PI3K and MAPK kinase inhibitors, LY294002, PD98059, SP600125, and SB202190, have been investigated on the sulforaphane-induced expression of thioredoxin reductase and thioredoxin. PD98059 abrogates the sulforaphane-induced thioredoxin reductase at both mRNA and protein levels in HepG2 cells, although other inhibitors were found less effective. However, both PD98059 and LY294002 significantly decrease thioredoxin mRNA expression in HepG2 cells. None of the inhibitors tested were able to modulate the level of expression of either thioredoxin reductase mRNA or protein in Caco-2 cells suggesting that there are cell-specific responses to sulforaphane. In summary, the dietary isothiocyanate, sulforaphane, is important in the regulation of thioredoxin reductase/thioredoxin redox system in cells.

Calculated free testosterone in men: comparison of four equations and with free androgen index.

BACKGROUND: Serum testosterone remains the most important investigation in the diagnosis of androgen deficiency in men. Most of the circulating testosterone is bound to albumin and sex hormone-binding globulin (SHBG), whereas free testosterone accounts for approximately 2% of total testosterone. Because direct measurement of free testosterone is impractical in routine practice, several equations are used to provide clinically useful estimates of free testosterone concentration. This study aimed to (1) obtain locally derived reference limits for total testosterone and calculated free testosterone (CFT) concentrations, and (2) critically evaluate the equations commonly used to estimate free testosterone. METHODS: Serum total testosterone, SHBG and albumin were assayed in morning blood samples obtained from 126 healthy men (aged 20-45 years) known to have normal semen analysis. CFT concentrations calculated using four published methods (i.e. the Sodergard, Nanjee-Wheeler, Vermeulen and Ly-Handelsman equations) were compared with one another and the free androgen index. RESULTS: Reference intervals for total testosterone and CFT by the Vermeulen equation were 9.4-31.0 nmol/L and 0.245-0.785 nmol/L (2.5-97.5 percentile), respectively. CFT values varied considerably with the four equations examined. Mean biases ranged from 5.8 to 56.0%; the Nanjee-Wheeler and Ly-Handelsman equations yielded positive and negative biases, respectively, against the other equations. Free androgen index was shown to correlate poorly with CFT (r2=0.21-0.46) and over-estimate the CFT at low SHBG concentrations. CONCLUSIONS: We have used various equations to derive reference ranges for CFT in healthy men aged 20-45 years. We suggest that CFT be incorporated into the investigation regimen for suspected hypogonadism when total testosterone results are equivocal.

Derivatization of estrogens enhances specificity and sensitivity of analysis of human plasma and serum by liquid chromatography tandem mass spectrometry.

Estrogens circulate at concentrations less than 20pg/mL in men and postmenopausal women, presenting analytical challenges. Quantitation by immunoassay is unreliable at these low concentrations. Liquid chromatography tandem mass spectrometry (LC-MS/MS) offers greater specificity and sometimes greater sensitivity, but ionization of estrogens is inefficient. Introduction of charged moieties may enhance ionization, but many such derivatives of estrogens generate non-specific product ions originating from the "reagent" group. Therefore an approach generating derivatives with product ions specific to individual estrogens was sought. Estrogens were extracted from human plasma and serum using solid phase extraction and derivatized using 2-fluoro-1-methylpyridinium-p-toluenesulfonate (FMP-TS). Electrospray in positive mode with multiple reaction monitoring using a QTrap 5500 mass spectrometer was used to quantify "FMP" derivatives of estrogens, following LC separation. Transitions for the FMP derivatives of estrone (E1) and estradiol (E2) were compound specific (m/z 362→238 and m/z 364→128, respectively). The limits of detection and quantitation were 0.2pg on-column and the method was linear from 1-400pg/sample. Measures of intra- and inter-assay variability, precision and accuracy were acceptable (<20%). The derivatives were stable over 24h at 10°C (7-9% degradation). Using this approach, E1 and E2, respectively were detected in human plasma and serum: pre-menopausal female serum (0.5mL) 135-473, 193-722pmol/L; male plasma (1mL) 25-111, 60-180pmol/L and post-menopausal female plasma (2mL), 22-78, 29-50pmol/L. Thus FMP derivatization, in conjunction with LC-MS/MS, is suitable for quantitative analysis of estrogens in low abundance in plasma and serum, offering advantages in specificity over immunoassay and existing MS techniques.

Selenium supplementation acting through the induction of thioredoxin reductase and glutathione peroxidase protects the human endothelial cell line EAhy926 from damage by lipid hydroperoxides.

The human endothelial cell line EAhy926 was used to determine the importance of selenium in preventing oxidative damage induced by tert-butyl hydroperoxide (tert-BuOOH) or oxidised low density lipoprotein (LDLox). In cells grown in a low selenium medium, tert-BuOOH and LDLox killed cells in a dose-dependent manner. At 555 mg/l LDLox or 300 microM tert-BuOOH, >80% of cells were killed after 20 h. No significant cell kill was achieved by these agents if cells were pre-incubated for 48 h with 40 nM sodium selenite, a concentration that maximally induced the activities of cytoplasmic glutathione peroxidase (cyGPX; 5.1-fold), phospholipid hydroperoxide glutathione peroxidase (PHGPX;1.9-fold) and thioredoxin reductase (TR; 3.1-fold). Selenium-deficient cells pre-treated with 1 microM gold thioglucose (GTG) (a concentration that inhibited 25% of TR activity but had no inhibitory effect on cyGPX or PHGPX activity) were significantly (P<0.05) more susceptible to tert-BuOOH toxicity (LC(50) 110 microM) than selenium-deficient cells (LC(50) 175 microM). This was also the case for LDLox. In contrast, cells pre-treated with 40 nM selenite prior to exposure to GTG were significantly more resistant to damage from tert-BuOOH and LDLox than Se-deficient cells. Treatment with GTG or selenite had no significant effect on intracellular total glutathione concentrations. These results suggest that selenium supplementation, acting through induction of TR and GPX, has the potential to protect the human endothelium from oxidative damage.

Selenium and endocrine systems.

The trace element selenium (Se) is capable of exerting multiple actions on endocrine systems by modifying the expression of at least 30 selenoproteins, many of which have clearly defined functions. Well-characterized selenoenzymes are the families of glutathione peroxidases (GPXs), thioredoxin reductases (TRs) and iodothyronine deiodinases (Ds). These selenoenzymes are capable of modifying cell function by acting as antioxidants and modifying redox status and thyroid hormone metabolism. Se is also involved in cell growth, apoptosis and modifying the action of cell signalling systems and transcription factors. During thyroid hormone synthesis GPX1, GPX3 and TR1 are up-regulated, providing the thyrocytes with considerable protection from peroxidative damage. Thyroidal D1 in rats and both D1 and D2 in humans are also up-regulated to increase the production of bioactive 3,5,3'-tri-iodothyronine (T3). In the basal state, GPX3 is secreted into the follicular lumen where it may down-regulate thyroid hormone synthesis by decreasing hydrogen peroxide concentrations. The deiodinases are present in most tissues and provide a mechanism whereby individual tissues may control their exposure to T3. Se is also able to modify the immune response in patients with autoimmune thyroiditis. Low sperm production and poor sperm quality are consistent features of Se-deficient animals. The pivotal link between Se, sperm quality and male fertility is GPX4 since the enzyme is essential to allow the production of the correct architecture of the midpiece of spermatozoa. Se also has insulin-mimetic properties, an effect that is probably brought about by stimulating the tyrosine kinases involved in the insulin signalling cascade. Furthermore, in the diabetic rat, Se not only restores glycaemic control but it also prevents or alleviates the adverse effects that diabetes has on cardiac, renal and platelet function.

Sulforaphane, erucin, and iberin up-regulate thioredoxin reductase 1 expression in human MCF-7 cells.

Isothiocyanates (ITCs) found in cruciferous vegetables are potentially important anticarcinogenic phytochemicals for many types of cancers including breast cancer. In this study, we have shown that three isothiocyanates, sulforaphane, erucin, and iberin, are potent inducers of thioredoxin reductase 1 (TrxR1) in human breast cancer MCF-7 cells. Sulforaphane, erucin, and iberin at 1 microM induce TrxR1 mRNA 2-3-fold within 8 h of treatment, and induce mRNA 5-7-fold with 12 microM ITC treatments. Selenium did not affect sulforaphane-induced TrxR1 mRNA levels, but significantly enhanced both TrxR1 protein expression (up to 9-fold in erucin treatment) and corresponding activities. These results suggest that dietary ITCs are important factors in the regulation of redox status through the induction of the selenoprotein thioredoxin reductase.

Selenium and the regulation of cell signaling, growth, and survival: molecular and mechanistic aspects.

In the past 30 years, it has been recognized that dietary selenium (Se) is essential for the normal function of many of the systems of the body. Furthermore, low Se intake can have deleterious effects on several aspects of human and animal health. The importance of Se is characterized in its role as a constituent of several key antioxidant and redox enzyme families. Most of the effects of Se are probably mediated by selenoproteins, which have the micronutrient covalently incorporated into the protein. The purpose of this review is to examine basic mechanisms by which Se regulates cell growth, gene transcription, cell signaling, and cell death. We start with the historical background to Se. The synthesis and function of selenoproteins are described, followed by details of the dietary sources of Se and Se status in different parts of the world, together with the clinical effects of Se deficiency and toxicity. We consider some aspects of the molecular mechanisms by which Se modulates cell growth, intracellular signaling, and gene transcription.

Discordance in thyroglobulin measurements by radioimmunoassay and immunometric assay: a useful means of identifying thyroglobulin assay interference.

BACKGROUND: Serum thyroglobulin (Tg) is useful for monitoring patients with differentiated thyroid cancer (DTC) but is limited by interference from anti-Tg antibodies (TgAb). We determined Tg assay discordance between a radioimmunoassay (RIA) and one of two immunometric assays (IMA) in DTC patients over a 9-year period to gauge assay performance against evidence of recurrent/progressive DTC. METHODS: Patients with DTC monitored for >1 year attending local clinics between September 2000 and January 2010 were included. All samples were analysed for Tg using both RIA and IMA. TgAb were measured on all Tg requests made after May 2006. Bias plots comparing RIA against IMA were established to calculate a 2-SD outlier limit. Clinical records were viewed to compare discordant Tg results against clinical evidence of recurrent/progressive DTC. RESULTS: Discordant Tg results were observed in 53/433 patients (12.2%). Four were discordant owing to a higher IMA result, one of which demonstrated recurrence. The remaining 49 patients demonstrated a disproportionately higher RIA result, of which four had recurrent/persistent disease. Twelve patients with a higher RIA result but no evidence of recurrence underwent thyrogen stimulation testing, which was negative in all 12. In many cases, assay discordance appeared more sensitive at indicating interference than direct measurement of TgAb. CONCLUSIONS: Interference was evident with both Tg assays, such that neither could be solely relied upon to provide the correct result in the presence of TgAb. The concomitant measurement of Tg by RIA and IMA methods should be considered as an alternative to monitoring TgAb status.

Elevated levels of the long pentraxin 3 in paracetamol-induced human acute liver injury.

OBJECTIVES: Pentraxin 3 (PTX3) is a long pentraxin with diverse humoral innate immune functions. The aims of this study were to measure levels of PTX3 and C-reactive protein (CRP), a hepatocyte-derived short pentraxin, in patients after acute liver injury. METHODS: PTX3 and CRP levels were measured in a total of 60 patients [48 paracetamol overdose (POD), 12 non-POD]. PTX3 expression was assessed by immunohistochemical analysis in explanted liver tissue. RESULTS: Admission PTX3 levels were significantly higher in POD acute liver failure (ALF) patients compared with POD non-ALF patients (P=0.0005) and non-POD patients (P=0.004). PTX3 levels in POD patients who died or required orthotopic liver transplantation (OLT, n=14) were significantly higher compared with those in spontaneous survivors (n=34, P=0.0011). The area under the receiver operator characteristic for PTX3 for death/OLT in POD patients was 0.80 (95% confidence interval 0.67-0.93). PTX3 levels were significantly higher in those POD patients who developed the systemic inflammatory response syndrome (P=0.001). Conversely, admission CRP levels were significantly lower in POD compared with non-POD patients (P=0.011), with no significant differences between survivors and nonsurvivors. After emergency OLT, PTX3 levels fell markedly; in contrast, CRP levels rapidly increased. Immunohistochemical analysis showed PTX3 expression in sinusoidal lining cells of a normal liver, infiltrating inflammatory cells in patients with ALF, and in a membranous distribution on injured hepatocytes in POD patients. CONCLUSION: Increased PTX3 levels are associated with adverse outcomes following POD, suggesting that the humoral innate immune system plays an underrecognized role in this condition.

Synergy between sulforaphane and selenium in the up-regulation of thioredoxin reductase and protection against hydrogen peroxide-induced cell death in human hepatocytes.

Dietary isothiocyanates and selenium are chemopreventive agents and potent inducers of antioxidant enzymes. It has been previously shown that sulforaphane and selenium have a synergistic effect on the upregulation of thioredoxin reductase-1 (TrxR-1) in human hepatoma HepG2 cells. In this paper, further evidence is presented to show that sulforaphane and selenium synergistically induce TrxR-1 expression in immortalised human hepatocytes. Sulforaphane was found to be more toxic toward hepatocytes than HepG2 cells with IC50=25.1 and 56.4 µM, respectively. Sulforaphane can protect against hydrogen peroxide-induced cell death and this protection was enhanced by co-treatment with selenium. Using siRNA to knock down TrxR-1 or Nrf2, sulforaphane (5 µM)-protected cell viability was reduced from 73% to 46% and 34%, respectively, suggesting that TrxR-1 is an important enzyme in protection against hydrogen peroxide-induced cell death. Sulforaphane-induced TrxR-1 expression was positively associated with significant levels of Nrf2 translocation into the nucleus, but co-treatment with selenium showed no significant increase in Nrf2 translocation. Moreover, MAPK (ERK, JNK and p38) and PI3K/Akt signalling pathways were found to play no significant role in sulforaphane-induced Nrf2 translocation into the nucleus. However, blocking ERK and JNK signalling pathways decreased sulforaphane-induced TrxR-1 mRNA by about 20%; whereas blocking p38 and PI3K/AKT increased TrxR-1 transcription. In summary, a combination of sulforaphane and selenium resulted in a synergistic upregulation of TrxR-1 that contributed to the enhanced protection against free radical-mediated oxidative damage in human hepatocytes.

Late-onset male hypogonadism: clinical and laboratory evaluation.

Late-onset male hypogonadism (LOH) is a clinical and biochemical syndrome associated with advancing age and characterised by low serum testosterone concentrations. An understanding of the physiology of androgens in the ageing man is essential for the appropriate diagnosis of LOH. Clinical assessment of androgen status relevant to clinical biochemists and chemical pathologists is outlined in this review. Laboratory investigations of androgen status in men are not without pitfalls and the authors highlight problems associated with measuring and calculating serum testosterone and its fractions, the interpretation of which can be problematic. Current clinical guidelines and recommendations regarding the diagnosis and monitoring of LOH are also summarised.

Mechanisms behind the non-thyroidal illness syndrome: an update.

The mechanisms behind the changes in serum triiodothyronine (T(3)), thyroxine (T(4)) and TSH that occur in the non-thyroidal illness syndrome (NTIS) are becoming clearer. Induction of a central hypothyroidism occurs due to a diminution in hypothalamic thyrotropin-releasing hormone. This can be signalled by a decrease in leptin caused by malnutrition and possibly a localised increase in hypothalamic T(3) catalyzed by altered expression of hypothalamic iodothyronine deiodinases D2 and D3. Data from D1 and D2 knockout mice suggest that these enzymes may have little contribution to the low serum T(3) found in acute illness. The decline in serum T(3) and T(4) in models of acute illness precedes the fall in hepatic D1, suggesting that much of the initial fall in these hormones may be attributable to an acute phase response giving rise to a reduction in the thyroid hormone binding capacity of plasma. When measured by reliable methods, changes in serum free T(4) and free T(3) are modest in comparison to the fall seen in total thyroid hormone. Thyroid hormone transporter expression is up-regulated in many models of the NTIS, thus if diminished tissue uptake of hormone occurs in vivo, it is likely to be the result of impaired transporter function caused by diminished intracellular ATP or plasma inhibitors of transporter action. In man, chronic illness leads to an upregulation of thyroid hormone receptor (THR) expression at least in liver and renal failure. In contrast, human and animal models of sepsis and trauma indicate that expression of THRs and their coactivators are decreased in acute illness.

Lack of effect of oral selenite on p53 associated gene expression during TL01 therapy of psoriasis patients.

Selenium (Se) has protective properties against ultraviolet (UV)-induced changes in skin cells in vitro but little is known about such activity in human subjects. In the present study, seven patients with psoriasis ingested 400 microg of sodium selenite daily during a 4 week course of whole-body narrow-band UVB (TL01) therapy while six more psoriasis patients, similarly irradiated, ingested a placebo. Skin biopsies, collected at the start and end of the phototherapy were analysed for phosphorylated p53, Fas, Bcl-2, Bax and oxidized guaninosine, and for numbers of Langerhans and sunburn cells. Following the TL01 therapy, no significant difference was observed for any of these markers when the Se group was compared with the placebo group of patients, although p53 and Bcl-2 expression decreased in the Se supplemented group.

Selenomethionine inhibits ultraviolet radiation-induced p53 transactivation.

BACKGROUND: Ultraviolet (UV) radiation damages the cellular DNA of skin cells. In response, wild-type p53 protein accumulates in irradiated cells and the stabilized and transactivated protein can then induce genes involved in cell cycle arrest in G1, or in the initiation of apoptosis. Selenium protects cells from UVB-induced cell death and apoptosis by mechanisms which are unclear, although recent reports suggest that selenium protects against UV-induced cell damage by inducing DNA repair enzymes and transactivating p53. METHODS: We examined whether selenomethionine could protect human skin cells from UV radiation-induced p53 transactivation, using a pRGCDeltafos-lacZ p53-dependent reporter construct stably transfected in an amelanotic melanoma cell line (Arn-8) which expresses wild-type p53. Cells were pretreated with or without selenomethionine and then irradiated with broadband UVB (approximately 270-350 nm); 0-30 mJ/cm2 from a Phillips TL100 W/12 lamp. RESULTS: The percentage of cells with transcriptionally active p53 increased dose dependently up to 20 mJ/cm2 UVB. Treatment with 50 microM selenomethionine for 24 h both pre- and post-irradiation, significantly diminished p53 activation by 30-43% across the UV dose range (P=0.0085, n=5 independent experiments) and decreased UV-induced p53 protein accumulation as assessed by Western blotting. CONCLUSIONS: We conclude that selenomethionine inhibits broad band UVB-induced p53 transactivation and protein accumulation and that this effect correlates with reported protective effects of selenium against UV-induced DNA damage.