Effect of acute adrenalectomy on rat liver glucocorticoid receptor

In order to improve current clinical treatment of human hypocortisolism, it is necessary to understand molecular aspects of this pathophysiology. In this study liver tissues from male Wistar rats were used as an experimental model to study structural and functional properties of glucocorticoid receptor (GR) in the absence of glucocorticoid hormones (GC). Results show that acute adrenalectomy (ADX) significantly increases the number of GR binding sites and GR protein content. In addition, acute ADX stimulates increase in stability of the GR, decrease in stability of the glucocorticoid- receptor complex (G-R), and changes in accumulation of the G-R complex in nuclei and its cellular distribution.

Molekulska osnova delovanja glikokortikoida

Glucocorticoid hormones are involved in regulation of cell processes and coordinate physiological response to diverse signals. These hormones, through interaction with specific intracellular receptors, coordinate components of physiological repertoires by activating the expression of gene networks. Thus hormone-receptor complexes may function as key constituent in regulation of specific cell functions as well as in provoking differentiation in already determined cells. Analysis of steroid receptors are important for understanding of molecular details of transcriptional control as well as providing the insight as to how an individual transcriptional factor such as glucocorticoid receptor, contributes to cell identity and function. The purpose of this review is to establish the general molecular mechanism of glucocorticoid action and mechanism associated hormone-receptor complexes with the control of differential patterns (i.e. "positive" and "negative") of gene expression. One of the examples of two signal pathways regulating opposite gene expression are NF-kB and GR-mediated signal pathways. These pathways have important and opposite roles in the immune function. NF-kB is transcription factor which induces the expression of many genes that participate in immune and inflamatory response, while GR is transcription factor that serves as antiinflammatory agent and immune suppressor. Their interactions within the cell, although not yet completely understood, appear to be an important, possibly even the primary mechanism of immune homeostasis. It has not been established that glucocorticoid sensitivity can be caused by mechanisms other than changes of GR number and properties, although recent studies have indicated that receptor isoforms and transcriptional factors may modulate glucocorticoid responsiveness by interacting with receptor protein or directly at the site of DNA binding. The aim of this review is also to describe the role of glucocorticoid receptors in mechanism of glucocorticoid action on cell functions, including immune responses, as well as to present emerging issues on clinical aspects of molecular mechanisms of glucocorticoid action.Glikokortikoidni hormoni su uključeni u regulaciju ćelijskih procesa koji koordiniraju fiziološke odgovore na različite signale. Ovi hormoni u kompleksu sa specifičnim ćelijskim receptorima preko aktivacije ekspresije mreže različitih gena učestvuju u koordinaciji komponenti koje su u osnovi fizioloških odgovora. Na taj način kompleksi hormona i receptora funkcionišu kao ključni faktor u regulaciji specifičnih ćelijskih funkcija, a takođe podstiču i procese diferencijacije u već determinisanim ćelijama. Analize glikokortikoidnih receptora (GR) su značajne, kako za bolje upoznavanje transkripcione kontrole, tako i za objašnjenje kako pojedini transkripcioni faktori, kao što su GR, doprinose identitetu ćelije i njenom funkcionisanju. U ovom radu su prikazani opšti principi molekulskog mehanizma delovanja glikokortikoida, kao i mehanizmi koji povezuju komplekse hormona i receptora sa kontrolom različitog tipa („pozitivnom” ili „negativnom”) genske ekspresije. Jedan od primera za signalne puteve koji suprotno regulišu aktivnost gena su nukleusni faktor kapaB (NFκB) i signalni putevi posredovani sa GR. Ovi putevi imaju suprotne uloge u regulaciji funkcionisanja imunskog sistema. NFκB je transkripcioni faktor koji indukuje ekspresiju gena uključenih u imunske i zapaljenjske procese. GR je takođe transkripcioni faktor, ali deluje kao antiinflamacioni i imunosupresivni agens. Njihove interakcije su značajne u ćelijama imunskog sistema, iako još nisu potpuno objašnjene; one su možda čak i primarne u mehanizmu imunske homeostaze. Do sada nije dokazano da ćelijska senzitivnost na delovanje glikokortikoida zavisi od mehanizama koji ne uključuju promene količine i funkcionalnih osobina GR. Međutim, novija istraživanja pokazuju da izoforme receptora i transkripcioni faktori mogu da menjaju ćelijski odgovor na glikokortikoide preko interakcije sa receptornim proteinom ili direktno sa mestima vezivanja na DNK. U ovom radu su takođe prikazani podaci iz literature o ključnoj ulozi glikokortikoidnih receptora u mehanizmu delovanja glikokortikoida u regulaciji ćelijskih funkcija, uključujući i ćelije imunskog sistema, kao i podaci o kliničkim aspektima molekulskog delovanja glikokortikoida

Gender modulates development of the metabolic syndrome phenotype in fructose-fed rats

We analyzed the effects of a fructose-rich diet (FRD) to test the assumption that the expression of metabolic syndrome phenotype is different in male and female rats. Two-way ANOVA revealed a significant effect of FRD on feeding behavior and carbohydrate/lipid metabolism. The increased caloric intake in FRD rats of both sexes was followed by a cluster of gender-specific changes typical for the metabolic syndrome. Female rats were characterized by decreased glycemia, increased triglycerides, enlarged visceral adipose tissue and increased absolute mass of liver, without changes in systolic blood pressure and insulin sensitivity. In contrast, male rats developed less disturbances in physical and biochemical characteristics, but blood pressure and insulin sensitivity were impaired by FRD. The results emphasize the detrimental effects of fructose consumption on cardiovascular risk and insulin action in males, whereas females are affected by other metabolic disturbances. These results support the idea of gender-dependent differences in the expression of the metabolic syndrome phenotype.Projekat ministarstva br. 4100

Does oestradiol attenuate the damaging effects of a fructose-rich diet on cardiac Akt/endothelial nitric oxide synthase signalling?

Fructose-rich diets (FRD) cause cardiac insulin resistance manifested by impairment of Akt/endothelial NO synthase (eNOS) signalling. In contrast, oestradiol (E2) activates this signalling pathway in the heart. To study the ability of E2 to revert the detrimental effect of fructose on cardiac Akt/eNOS, female rats were subjected to a FRD and ovariectomy followed with or without E2 replacement. We also analysed the effects of the FRD and E2 on cardiac extracellular signal-regulated kinase (Erk 1/2) signalling related to their role in cardiac hypertrophy development. Expression of Akt, eNOS and Erk 1/2, as well as regulatory phosphorylations of these molecules were determined. The protein expression of cardiac Akt and eNOS was not affected by the diet or E2 treatment. However, the FRD was accompanied by a decrease in Akt phosphorylation at Ser(473) and Thr(308), and eNOS at Ser(1177), while the phosphorylation of eNOS at Thr(495) was increased. E2 replacement in ovariectomised fructose-fed rats caused a reversion of the diet effect on Akt and eNOS serine phosphorylation, but mostly had no effect on threonine phosphorylation of the molecules. The FRD and E2 treatment did not influence Erk 1/2 expression and phosphorylation and heart mass as well. The data show that E2 selectively suppress the negative effects of a FRD on Akt/eNOS signalling and probably point to the different effects of E2 on kinase/phosphatase pathways responsible for phosphorylation/dephosphorylation of Akt and eNOS. Furthermore, the results suggest that the heart of females in the reproductive period is partially protected against the damaging effects of increased fructose intake

Measles situation in Serbia in an era of measles elimination (2007-2009)

Following the introduction of measles immunization in Serbia in 1971, measles outbreaks were recorded every 3 to 5 years until 1997. The outbreak in 1997 with 4000 cases was the last large outbreak in Serbia. In 2007, an outbreak with 191 laboratory confirmed or epidemiologically linked cases was reported in Vojvodina. In 2008 and 2009, only 3 cases were confirmed. From 2007-2009, measles infections were most frequently detected in the Roma population but also in non-immunized or partially immunized persons from the general population

Gender modulates development of the metabolic syndrome phenotype in fructose-fed rats

We analyzed the effects of a fructose-rich diet (FRD) to test the assumption that the expression of metabolic syndrome phenotype is different in male and female rats. Two-way ANOVA revealed a significant effect of FRD on feeding behavior and carbohydrate/lipid metabolism. The increased caloric intake in FRD rats of both sexes was followed by a cluster of gender-specific changes typical for the metabolic syndrome. Female rats were characterized by decreased glycemia, increased triglycerides, enlarged visceral adipose tissue and increased absolute mass of liver, without changes in systolic blood pressure and insulin sensitivity. In contrast, male rats developed less disturbances in physical and biochemical characteristics, but blood pressure and insulin sensitivity were impaired by FRD. The results emphasize the detrimental effects of fructose consumption on cardiovascular risk and insulin action in males, whereas females are affected by other metabolic disturbances. These results support the idea of gender-dependent differences in the expression of the metabolic syndrome phenotype.Projekat ministarstva br. 4100

EFFECT OF ACUTE ADRENALECTOMY ON RAT LIVER GLUCOCORTICOID RECEPTOR

Abstract- In order to improve current clinical treatment of human hypocortisolism, it is necessary to understand molecular aspects of this pathophysiology. In this study liver tissues from male Wistar rats were used as an experimental model to study structural and functional properties of glucocorticoid receptor (GR) in the absence of glucocorticoid hormones (GC). Results show that acute adrenalectomy (ADX) significantly increases the number of GR binding sites and GR protein content. In addition, acute ADX stimulates increase in stability of the GR, decrease in stability of the glucocorticoid-receptor complex (G-R), and changes in accumulation of the G-R complex in nuclei and its cellular distribution. Key words: Adrenalectomy, glucocorticoid receptor, number of binding sites, receptor protein content, stability of glucocorticoid-receptor complex, nuclear translocation. UDC 616.453-089.8:59]:577.

Insulin modulates rat liver glucocorticoid receptor

This investigation used cytosol fraction of rat liver to examine the effects of insulin ( INS) on functional properties of glucocorticoid receptor ( GR). Male Wistar rats ( 220 - 250 g b.wt.) were injected with INS ( 50 mu g/200 g b.wt, i.p.) and 18 h after INS administration used for experiments. INS-stimulated dissociation of G-R complexes was significantly increased by 133% compared to control level. However, INS treatment significantly stimulated stability of GR protein by 138% above control value. Furthermore, results show that INS stimulated activation of formed cytosol [ H-3] TA-R complexes by 143% in respect to control. [ H-3] TA-R complexes from INS treated animals could be activated and accumulated at higher rate in cell nuclei of control animals. The physiological relevance of the data was confirmed by INS-related stimulation of Tryptophan oxigenase ( TO) activity. It was observed that INS stimulated TO activity while INS injected to adrenalectomized rats, exhibited less effects compared to control. The results indicate that a glucocorticoid hormone ( CORT) enhances INS induced stimulation of TO activity, as evidenced by enhanced enzyme activity. Presented data suggest: that INS treatment leads to modifications of the GR protein and the nuclear components and that INS activates the rat liver CORT signaling pathway which mediates, in part, the activity of TO

Role of ERK1/2 Activation In Thrombin-Induced Vascular Smooth Muscle Cell Hypertrophy

It is well recognized that the proliferation of vascular smooth muscle cells (VSMCs) is a key event in the pathogenesis of various vascular diseases, including atherosclerosis and hypertension. It is generally considered that the phosphorylation/dephosphorylation reactions of a variety of enzymes belonging to the family of mitogen-activated protein kinases (MAPKs) play an important role in the transduction of mitogenic signal. We have previously shown that among extracellular signal-regulated protein kinases (ERKs), the 42 and 44 kDa isoforms (ERK1/2) participate in the cellular mitogenic machinery triggered by several VSMCs activators, including thrombin. ERK1/2 activation by G-protein-coupled receptors (GPCRs) has been shown to be Ca2--dependent and to require the transactivation of epidermal growth factor receptor (EGFR). In addition, it is generally admitted that variations of the intracellular Ca2- concentration ([Ca2-] i) play an important role in the transduction of mitogenic signal. Recently, we have shown that in thrombin-stimulated VSMCs, EGFR-independent activation of ERK1/2 activation could occur when agonist-induced ([Ca2-] i) elevation was reduced. This review examines recent findings in ERK1/2 signaling pathway that have been identified as critically important mediator of VSMCs hypertrophy and vascular diseases. Future investigations should now focus on the mechanisms of MAPK activation which might therefore represent a new mechanism involved in the antiproliferative effect revealed in this review

Regulation of the inducible nitric oxide synthase and sodium pump in type 1 diabetes

Insulin-like growth factor-1 (IGF-1) is a hormone and growth factor closely related to insulin. The autocrine/paracrine actions of IGF-1 involve activation of inducible nitric oxide synthase (iNOS) and the Na(+), K(+)-ATPase sodium pump in cardiovascular tissues. Data from literature indicate that iNOS is expressed in vascular smooth muscle cells (VSMC) and that IGF- 1 -induced release of NO is both rapid and delayed. We hypothesize that impaired IGF-1 -induced sodium pump activity/ expression in rats with type 1 diabetes is related to activation of phosphatidytinositol 3 kinase (PI3K)/cytosolic phospholipase 2 (cPLA(2))/protein kinase B (Akt) signaling, and that IGF-1 prevents acute and chronic dysfunction of iNOS and sodium pump activity in a chemically induced model of type 1 diabetes, the streptozotocin -treated rat heart (STZ). Understanding how iNOS and sodium pump activity are regulated by IGF-1 activation of the PI3K/cPLA(2)/Akt cascade should provide novel and fundamental knowledge regarding the regulatory actions of IGF-1 in promoting vasodilation. Since insulin resistance is currently a major focus of research, the use of IGF-1 to improve insulin resistance and glucose metabolism has opened a new arena for treatment of comorbid conditions. Future investigations should now focus on mechanisms of action of IGF-1 and its clinical applicability. (c) 2007 Elsevier Ltd. All rights reserved