Aryl hydrocarbon receptor (AhR) and glucocorticoid receptor (GR) play crucial role in the regulation of drug metabolizing enzymes and in many essential physiological processes. Cellular signaling by these receptors shares several functional and regulatory features. Here we investigated regulatory cross-talk between these two receptors. Human hepatoma cells (HepG2) were the model of choice. We analyzed the effects of dexamethasone (DEX) and dioxin (TCDD) on i) expression of AhR and GRα mRNAs; ii) levels of AhR and GR proteins; iii) transcriptional activities of AhR and GR in reporter assays; iv) 7-ethoxyresorufin-O-deethylase activity (EROD). We found that both DEX and TCDD affected AhR and GR mRNAs expression, proteins levels and transcriptional activities in HepG2 cells. These effects on cellular signaling by AhR and GR comprised up-/down-regulation of gene expression and ligand-dependent protein degradation. We conclude that interactive regulatory cross-talk between GR and AhR receptors in HepG2 cells defines possible implications in physiology and drug metabolism. Future research should be focused on the investigation of AhR-GR cross-talk in various normal human cells and tissues both in vitro and in vivo., Z. Dvořák, R. Vrzal, P. Pávek, J. Ulrichová., and Obsahuje bibliografii a bibliigrafické odkazy
The thymus plays a critical role in establishing and maintaining the peripheral T-cell pool. It does so by providing a microenvironment within which T-cell precursors differentiate and undergo selection processes to create a functional population of major histocompatibility complex-restricted, self-tolerant T cells. These cells are central to adap tive immunity. Thymic T-cell development is influenced by loca lly produced soluble factors and cell-to-cell interactions, as well as by sympathetic noradrenergic and endocrine system signalling. Thymic lymphoid and non- lymphoid cells have been shown not only to express β - and α 1 - adrenoceptors (ARs), but also to synthesize catecholamines (CAs). Thus, it is suggested that CAs influence T-cell development via both neurocrine/endocrine and autocrine/ paracrine action, and that they serve as immunotransmitters between thymocytes and nerves. CAs acting at multiple sites along the thymocyte developmental route affect T-cell generation not only numerically, but also qualitatively. Thymic CA level and synthesis, as well as AR expression exhibit sex steroid-mediated sexual dimorphism. Moreover, the influence of CAs on T-cell development exhibits glucocorticoid-dependent plasticity. This review summarizes recent findings in this field and our current understanding of complex and multifaceted neuroendocrine- immune communications at thymic level., G. Leposavić, I. Pilipović, M. Perišić., and Obsahuje bibliografii a bibliografické odkazy
Clinical reports suggest close interactions between stressors, particularly those of long duration, and liver diseases, such as hepatic inflammation, that is proposed to occur via reactive oxygen species. In the present study we have used 21-day social isolation of male Wistar rats as a model of chronic stress to investigate protein expression/activity of liver antioxidant enzymes: superoxide dismutases (SODs), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GLR), and protein expression of their upstream regulators: glucocorticoid receptor (GR) and nuclear factor kappa B (NFkB). We have also characterized these parameters in either naive or chronically stressed animals that were challenged by 30-min acute immobilization. We found that chronic isolation caused decrease in serum corticosterone (CORT) and blood glucose (GLU), increase in NFkB signaling, and disproportion between CuZnSOD, peroxidases (CAT, GPx) and GLR, thus promoting H2O2 accumulation and prooxidative state in liver. The overall results suggested that chronic stress exaggerated responsiveness to subsequent stressor at the level of CORT and GLU, and potentiated GLR response, but compromised the restoration of oxido-reductive balance due to irreversible alterations in MnSOD and GPx., J. Djordjevic ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
This investigation addresses the interaction of insulin (INS) and glucocorticoid (GC) signaling in the hepatic regulation of tryptophan oxygenase (TO) enzyme activity in the rat. Male Wistar rats (200-250 g b.w) received an injection of the different doses of INS (10, 25, 50, 70 and 100 μg/200 g b.w., i.p.) and were used for experiments 3 h and 18 h after INS administration. This study shows that maximum of TO activity was found at dose of 50 μg of INS with peak increases observed at 3 h and 18 h after injection of INS, while INS had no effect on TO activity in adrenalectomized rats. The analysis of INS effects on glucocorticoid receptor-complex (GC/GR complex) stability shows that complexes from INS-treated rats are less stable than those from control animals. In addition, INS-stimulated stability of glucocorticoid receptor (GR) protein was significantly increased from the controls. Furthermore, the results show that GC/GR complexes from INS-treated rats could be activated and accumulated at higher rate in cell nuclei of control animals. These data support the involvement of INS in modulation of GC signaling pathway which mediates, in part, the activity of TO., E. R. Isenović, Z. Zakula, G. Koricanac, N. Ribarac-Stepić., and Obsahuje bibliografii a bibliografické odkazy
Many stress conditions are ac companied by skeletal muscle dysfunction and regeneration, which is essentially a recapitulation of the embryonic development. However, regeneration usually occurs under conditions of hypo thalamus-pituitary -adrenal gland axis activation and therefore incr eased glucocorticoid (GC) levels. Glucocorticoid receptor (GR), the main determinant of cellular responsiveness to GCs, exists in two isoforms (GRα and GRβ ) in humans. While the role of GR α is well characterized, GRβ remains an elusive player in GC si gnalling. To elucidate basic characteristics of GC signalling in the regenerating human skeletal muscle we assessed GRα and GCβ expression pattern in cultured human myoblasts and myotubes and their response to 24-hour dexamethasone (DEX) treatment. There was no difference in GRα mRNA and protein expression or DEX-mediated GRα down-regulation in myoblasts and myotubes. GRβ mRNA level was very low in myoblasts and remained unaffected by differentiation and/or DEX. GRβ protein could not be detected. These results indicate that response to GCs is established very early during human skeletal muscle regeneration and that it remains practically unchanged before innervation is established. Very low GRβ mRNA expression and inability to detect GRβ protein suggests that GRβ is not a major player in the early stages of human skeletal muscle regeneration., D. Filipović ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Through their receptors at each level of hypothalamo-pituitarygonadal axis glucocorticoid excess, either endogenous or administered or stress-induced, could affect steroid production in the testis and thus male fertility. The main ways by which glucocorticoids act are as follows: 1) Affecting gonadoliberin and LH synthesis and release through glucocorticoid receptors in hypothalamic neurons and pituitary gonadotropes. 2) By so far not clearly evidenced reduction of the number of LH receptors on the membrane of Leydig cells. 3) By affecting expression and function of steroidogenic enzymes in the testis. 4) By regulation of in situ access of glucocorticoid to its target cells in the testis. 5) By promotion Leydig cell apoptosis. The review provides a survey of physiological and molecular mechanisms staying behind these effects. It does not deal with the clinical effects of glucocorticoid treatment which would substantially exceed the scope of the pater., Richard Hampl, Luboslav Stárka., and Obsahuje bibliografii
The aim of the present study was to define the stress-induced pattern of cytosolic glucocorticoid receptor (GR) and Hsp70 protein in the liver of male Wistar rats exposed to different stress models: acute (2 h/day) immobilization or cold (4 °C); chronic (21 days) isolation, crowding, swimming or isolation plus swimming and combined (chronic plus acute stress). Changes in plasma levels of corticosterone were studied by radioimmunoassay (RIA). The results obtained by Western immunoblotting showed that both acute stressors led to a significant decrease in cytosolic GR and Hsp70 levels. Compared to acute stress effects, only a weak decrease in the levels of GR and Hsp70 was demonstrated in chronic stress models. Chronically stressed rats, which were subsequently exposed to novel acute stressors (immobilization or cold), showed a lower extent of GR down-regulation when compared to acute stress. The exception was swimming, which partially restores this down-regulation. The observed changes in the levels of these major stress-related cellular proteins in liver cytosol lead to the conclusion that chronic stressors compromise intracellular GR down-regulation in the liver., D. Filipović, L. Gavrilović, S. Dronjak, M. Demajo, M. B. Radojčić., and Obsahuje bibliografii a bibliografické odkazy
Abnormal accumulation of lymphoblasts in the blood and bone marrow is the main characteristic of acute lymphoblastic leukaemia (ALL). Glucocorticoids are effective drugs for ALL, while glucocorticoid resistance is an obstacle to ALL therapy. MicroRNAs (miRNAs) are implicated in the drug resistance and modulate the response of ALL to glucocorticoids. The role of miR-503 in glucocorticoid sensitivity of ALL was investigated in this study. Firstly, T-leukaemic cells were isolated from patients with ALL. The human ALL cell line (CCRF/CEM) was incubated with dexamethasone to establish a glucocorticoid- resistant ALL cell line (CCRF/CEM-R). Data from MTT showed that IC50 (50% inhibitory concentration) of dexamethasone in T-leukaemic cells isolated from glucocorticoid-resistant ALL patients or CCRF/CEM-R was increased compared with IC50 in T-leukaemic cells isolated from glucocorticoid- sensitive ALL patients or CCRF/CEM. MiR- 503 was down-regulated in glucocorticoid-resistant leukaemic cells and CCRF/CEM-R. Secondly, overexpression of miR-503 sensitized CCRF/CEM-R to dexamethasone. Moreover, over-expression of miR- 503 also promoted the sensitivity of ALL cells to dexamethasone. Thirdly, miR-503 bound to WNT3A mRNA and negatively regulated the expression of WNT3A. Over-expression of miR-503 reduced protein expression of nuclear β-catenin, and over-expression of WNT3A attenuated the miR-503 overexpression- induced decrease in nuclear β-catenin. Lastly, the over-expression of miR-503-induced increased sensitivity of ALL-resistant cells and CCRF/ CEM-R to dexamethasone was attenuated by overexpression of WNT3A. In conclusion, miR-503 targeted WNT3A mRNA to sensitize ALL cells to glucocorticoids through inactivation of the Wnt/β-catenin pathway.
Resistance to steroid hormones presents a serious problem with respect to their mass use in therapy. It may be caused genetically by mutation of genes involved in hormonal signaling, not only steroid receptors, but also other players in the signaling cascade as co-regulators and other nuclear factors, mediating the hormone-born signal. Another possibility is acquired resistance which may develop under long-term steroid treatment, of which a particular case is down regulation of the receptors. In the review recent knowledge is summarized on the mechanism of main steroid hormone action, pointing to already proven or potential sites causing steroid resistance. We have attempted to address following questions: 1) What does stay behind differences among patients as to their response to the (anti)steroid treatment? 2) Why do various tissues/cells respond differently to the same steroid hormone though they contain the same receptors? 3) Are such differences genetically dependent? The main attention was devoted to glucocorticoids as the most frequently used steroid therapeutics. Further, androgen insensitivity is discussed with a particular attention to acquired resistance to androgen deprivation therapy of prostate cancer. Finally the potential causes are outlined of breast and related cancer(s) resistance to antiestrogen therapy., R. Hampl, K. Vondra., and Obsahuje bibliografii
Maternal hyperandrogenism during pregnancy might have metabolic and endocrine consequences on the offspring as shown for the polycystic ovary syndrome. Despite numerous experiments, the impact of prenatal hyperandrogenic environment on postnatal sex steroid milieu is not yet clear. In this study, we investigated the effect of prenatal testosterone excess on postnatal concentrations of luteinizing hormone, corticosterone and steroid hormones including testosterone, pregnenolone, progesterone, estradiol and 7β-hydroxyepiandrosterone in the offspring of both sexes. Pregnant rats were injected daily with either testosterone propionate or vehicle from gestational day 14 until parturition. The hormones were evaluated in plasma of the adult offspring. As expected, females had lower testosterone and higher pregnenolone, progesterone and estradiol in comparison to males. In addition, corticosterone was higher in females than in males, and it was further elevated by prenatal testosterone treatment. In males, prenatal testosterone exposure resulted in higher 7β-hydroxyepiandrosterone in comparison to control group. None of the other analyzed hormones were affected by prenatal testosterone. In conclusion, our results did not show major effects on sex hormone production or luteinizing hormone release in adult rats resulting from testosterone excess during their fetal development. However, maternal hyperandrogenism seems to partially affect steroid biosynthesis in sex-specific manner., E. Domonkos, V. Borbélyová, L. Kolátorová, T. Chlupáčová, D. Ostatníková, J. Hodosy, L. Stárka, P. Celec., and Obsahuje bibliografii