Estradiol decreases IGF-1 and IGF-1 receptor expression in rat aortic smooth muscle cells. Mechanisms for its atheroprotective effects

Cholecystokinin-mediated effect of insulin pathway on the steroidogenic activity of follicular granulosa cells in Camelus bactrianus: In vitro study

The current study aimed to explore the molecular mechanism by which the cholecystokinin (CCK)-mediated CCKAR and CCKBR, as well as the molecular mechanisms of CCK-mediated insulin signalling pathway, regulate oestrogen in the granulosa cells. Also, the expression of CCK in ovaries, uterus, hypothalamus and pituitary gland was investigated in Camelus bactrianus. Ovaries, uterus, hypothalamus and pituitary gland were collected from six, three before ovulation (control) and three after ovulation, slaughtered Camelus bactrianus. Ovulation was induced by IM injection of seminal plasma before slaughtering in the ovulated group. The results showed that there were differences in the transcription and protein levels of CCK in various tissues before and after ovulation (p < .05, p < .01). After transfection with p-IRES2-EGFP-CCK, the mRNA and protein levels of CCK, CCKAR, CCKBR and ER in follicular granulosa cells were significantly upregulated (p < .05, p < .01), and the content of E2 was significantly upregulated (p < .01); On the contrary, after transfection with si-CCK, the mRNA and protein levels of CCK, CCKAR, CCKBR and ER in follicular granulosa cells were significantly downregulated (p < .05, p < .01), and the content of E2 was significantly downregulated (p < .01). Regulating CCK can affect the mRNA levels of INS, INSR, IGF and IGF-R. In summary, regulating the expression level of CCK can activate insulin-related signalling pathways by CCKR, thereby regulating the steroidogenic activity of granulosa cells.

Cooperative interaction between ERα and the EMT-inducer ZEB1 reprograms breast cancer cells for bone metastasis

The epithelial to mesenchymal transition (EMT) has been proposed to contribute to the metastatic spread of breast cancer cells. EMT-promoting transcription factors determine a continuum of different EMT states. In contrast, estrogen receptor α (ERα) helps to maintain the epithelial phenotype of breast cancer cells and its expression is crucial for effective endocrine therapies. Determining whether and how EMT-associated transcription factors such as ZEB1 modulate ERα signaling during early stages of EMT could promote the discovery of therapeutic approaches to suppress metastasis. Here we show that, shortly after induction of EMT and while cells are still epithelial, ZEB1 modulates ERα-mediated transcription induced by estrogen or cAMP signaling in breast cancer cells. Based on these findings and our ex vivo and xenograft results, we suggest that the functional interaction between ZEB1 and ERα may alter the tissue tropism of metastatic breast cancer cells towards bone.

The epithelial mesenchymal transition (EMT) is important in the metastatic spread of cancer cells. Here, the authors show that the EMT transcription factor, ZEB1, can modify estrogen receptor α during EMT and facilitate the migration of breast cancer cells to the bone

Estradiol and Estrogen-like Alternative Therapies in Use: The Importance of the Selective and Non-Classical Actions

Estrogen is one of the most important female sex hormones, and is indispensable for reproduction. However, its role is much wider. Among others, due to its neuroprotective effects, estrogen protects the brain against dementia and complications of traumatic injury. Previously, it was used mainly as a therapeutic option for influencing the menstrual cycle and treating menopausal symptoms. Unfortunately, hormone replacement therapy might be associated with detrimental side effects, such as increased risk of stroke and breast cancer, raising concerns about its safety. Thus, tissue-selective and non-classical estrogen analogues have become the focus of interest. Here, we review the current knowledge about estrogen effects in a broader sense, and the possibility of using selective estrogen-receptor modulators (SERMs), selective estrogen-receptor downregulators (SERDs), phytoestrogens, and activators of non-genomic estrogen-like signaling (ANGELS) molecules as treatment.

High expression of SMYD3 indicates poor survival outcome and promotes tumour progression through an IGF-1R/AKT/E2F-1 positive feedback loop in bladder cancer

The AKT/mTOR pathway is critical for bladder cancer (BC) pathogenesis and is hyper-activated during BC progression. In the present study, we identified a novel positive feedback loop involving oncogenic factors histone methyltransferase SMYD3, insulin-like growth factor-1 receptor (IGF-1R), AKT, and E2F-1. SMYD3 expression was significantly up-regulated in BC tumors and positively associated with histological grade, lymph node metastasis, and shorter patient survival. Depletion of SMYD3 inhibited BC cell proliferation, colony formation, migration, invasion, and xenograft tumor growth. Mechanistically, SMYD3 inhibition led to the diminished AKT/mTOR signaling activity, thereby triggering deleterious effects on BC cells. Furthermore, SMYD3 directly activates the expression of IGF-1R, a critical activator of AKT in BC, by inducing hyper-methylation of histone H3-K4 and subsequent chromatin remodeling in the IGF-1R promoter region. On the other hand, E2F-1, a downstream factor of the AKT pathway, binds to the E2F-1 binding motifs at the SMYD3 promoter and consequently induces SMYD3 transcription and expression. Thus, SMYD3/IGF-1R/AKT/E2F-1 forms a positive feedback loop leading to the hyper-activated AKT signaling. Our findings provide not only profound insights into SMYD3-mediated oncogenic activity but also present a unique avenue for treating BC by directly disrupting this signaling circuit.

Vps11 and Vps18 of Vps-C membrane traffic complexes are E3 ubiquitin ligases and fine-tune signalling

In response to extracellular signals, many signalling proteins associated with the plasma membrane are sorted into endosomes. This involves endosomal fusion, which depends on the complexes HOPS and CORVET. Whether and how their subunits themselves modulate signal transduction is unknown. We show that Vps11 and Vps18 (Vps11/18), two common subunits of the HOPS/CORVET complexes, are E3 ubiquitin ligases. Upon overexpression of Vps11/Vps18, we find perturbations of ubiquitination in signal transduction pathways. We specifically demonstrate that Vps11/18 regulate several signalling factors and pathways, including Wnt, estrogen receptor α (ERα), and NFκB. For ERα, we demonstrate that the Vps11/18-mediated ubiquitination of the scaffold protein PELP1 impairs the activation of ERα by c-Src. Thus, proteins involved in membrane traffic, in addition to performing their well-described role in endosomal fusion, fine-tune signalling in several different ways, including through ubiquitination.

[Association between IGF system and PAPP-A in coronary atherosclerosis]

Atherosclerosis is a condition that involves multiple pathophysiological mechanisms and whose knowledge has not been fully elucidated. Often, scientific advances on the atherogenic pathophysiology generate that molecules not previously considered in the scene of this disease, were attributed actions on the onset or progression of it. A representative example is the study of a new mechanism involved in the atherogenic process, consisting of the association between the insulin-like growth factor (IGF) system and pregnancy-associated plasma protein-A (PAPP-A). Insulin-like growth factor system is a family of peptides that include 3 peptide hormones, 4 transmembrane receptors and 6 binding proteins. Insulin-like growth factor-1 (IGF-1) is the main ligand of the IGF system involved in coronary atherosclerosis. IGF-1 exerts its effects via activation of the IGF-1R receptor on vascular smooth muscle cells or macrophages. In vascular smooth muscle cells promotes migration and prevents apoptosis which increases plaque stability while in macrophages reduces reverse cholesterol transport leading to the formation of foam cells. Regulation of IGF-1 endothelial bioavailability is carried out by IGFBP proteases, mainly by PAPP-A. In this review, we address the mechanisms between IGF system and PAPP-A in atherosclerosis with emphasis on molecular effects on vascular smooth muscle cells and macrophages.

The effects of ovariectomy on meat performance and expression of GH/IGF-I in young goats

Zhang, L., Wang, Y.-y., Fu, M.-z., Li, G., An, N., Li, S.-y. and Zhou, Z.-q. 2014. The effects of ovariectomy on meat performance and expression of GH/IGF-I in young goats. Can. J. Anim. Sci. 94: 619–626. Experiments were carried out to investigate the effects of ovariectomy on meat production efficiency and to explore the expression of GH/IGF-I in young goats. Animal performance, meat quality, levels of serum growth hormone (GH) and insulin-like growth factor 1 (IGF-I), and mRNA levels of three key genes [GH Receptor (GHR), IGF-I and IGF-I Receptor (IGF-IR)] in longissimus dorsi and biceps femoris muscles were measured. The results show that carcass weight, net meat mass, fat weight and loin eye area of ovariectomized goats were higher than those of the controls, and ovariectomized goats lost 0.40 kg of bone weight (P<0.05). There was no statistically valid difference for the color, pH, water-holding capacity, or cooking rate of meat (P>0.05) between the two groups, except for the shear value, which was significantly lower in the Ovx group than in the control group (P<0.05). The results of this research show for the first time a significant trend (P<0.05) for serum GH and IGF-I in the direction of increasing in ovariectomized goats. Furthermore, the mRNA levels of GHR, IGF-I and IGF-IR in muscle were all up-regulated, except for the IGF-I gene in biceps femoris, by ovariectomy. In summary, ovariectomy showed a beneficial promotion in animal performance, but did not reduce meat quality, and increased serum GH and IGF-I and mRNA expression levels of GHR, IGF-I and IGF-IR in young female goats.

Effects of estradiol on transcriptional profiles in atherosclerotic iliac arteries in ovariectomized cynomolgus macaques

OBJECTIVE

This study aimed to assess the in vivo effects of estradiol treatment on arterial gene expression in atherosclerotic postmenopausal female monkeys.

METHODS

Eight ovariectomized cynomolgus monkeys were fed atherogenic diets for 6.5 years. The left iliac artery was biopsied before randomization to the estradiol group (human equivalent dose of 1 mg/d, n = 4) or the vehicle group (n = 4) for 8 months. The right iliac artery was obtained at necropsy. Transcriptional profiles in pretreatment versus posttreatment iliac arteries were compared to assess the responses of atherosclerotic arteries to estradiol.

RESULTS

Iliac artery plaque size did not differ between the estradiol group and the placebo group at baseline or during the treatment period. Nevertheless, estradiol treatment was associated with increased expression of 106 genes and decreased expression of 26 genes in the iliac arteries. Estradiol treatment increased the expression of extracellular matrix genes, including the α1 chain of type I collagen, the α2 chain of type VI collagen, and fibulin 2, suggestive of an increase in the proportion or phenotype of smooth muscles or fibroblasts in lesions. Also increased were components of the insulin-like growth factor pathway (insulin-like growth factor 1, insulin-like growth factor binding protein 4, and insulin-like growth factor binding protein 5) and the Wnt signaling pathway (secreted frizzled-related protein 2, secreted frizzled-related protein 4, low-density lipoprotein receptor-related protein 6, and Wnt1-inducible signaling pathway protein 2).

CONCLUSIONS

Estradiol treatment of monkeys with established atherosclerosis affected iliac artery gene expression, suggesting changes in the cellular composition of lesions. Moreover, it is probable that the presence of atherosclerotic plaque affected the gene expression responses of arteries to estrogen.

Circulating tumor cell identification by functionalized silver-gold nanorods with multicolor, super-enhanced SERS and photothermal resonances

Nanotechnology has been extensively explored for cancer diagnostics. However, the specificity of current methods to identify simultaneously several cancer biomarkers is limited due to color overlapping of bio-conjugated nanoparticles. Here, we present a technique to increase both the molecular and spectral specificity of cancer diagnosis by using tunable silver-gold nanorods with narrow surface-enhanced Raman scattering (SERS) and high photothermal contrast. The silver-gold nanorods were functionalized with four Raman-active molecules and four antibodies specific to breast cancer markers and with leukocyte-specific CD45 marker. More than two orders of magnitude of SERS signal enhancement was observed from these hybrid nanosystems compared to conventional gold nanorods. Using an antibody rainbow cocktail, we demonstrated highly specific detection of single breast cancer cells in unprocessed human blood. By integrating multiplex targeting, multicolor coding, and multimodal detection, our approach has the potential to improve multispectral imaging of individual tumor cells in complex biological environments.

Computational modelling of bovine ovarian follicle development

Background

The development of ovarian follicles hinges on the timely exposure to the appropriate combination of hormones. Follicle stimulating hormone (FSH) and luteinizing hormone (LH) are both produced in the pituitary gland and are transported via the blood circulation to the thecal layer surrounding the follicle. From there both hormones are transported into the follicle by diffusion. FSH-receptors are expressed mainly in the granulosa while LH-receptors are expressed in a gradient with highest expression in the theca. How this spatial organization is achieved is not known. Equally it is not understood whether LH and FSH trigger distinct signalling programs or whether the distinct spatial localization of their G-protein coupled receptors is sufficient to convey their distinct biological function.

Results

We have developed a data-based computational model of the spatio-temporal signalling processes within the follicle and (i) predict that FSH and LH form a gradient inside the follicle, (ii) show that the spatial distribution of FSH- and LH-receptors can arise from the well known regulatory interactions, and (iii) find that the differential activity of FSH and LH may well result from the distinct spatial localisation of their receptors, even when both receptors respond with the same intracellular signalling cascade to their ligand.

Conclusion

The model integrates the large amount of published data into a consistent framework that can now be used to better understand how observed defects translate into failed follicle maturation.

The insulin-like growth factor system, metabolic syndrome, and cardiovascular disease risk

The metabolic syndrome is a combination of metabolic and clinical features that aggregate in individuals and increase cardiovascular disease (CVD) risk considerably. It is believed, although sometimes controversially, that the underlying basis for this syndrome is insulin resistance (IR) and accompanying compensatory hyperinsulinemia. Insulin and insulin-like growth factors (IGFs) have significant homology and interact with differing affinity with the same receptors. Therefore, their actions can be complementary, and this becomes particularly significant clinico-pathologically when their circulating levels are altered. This review of currently available information attempts to answer the following questions: (1) Is there any evidence for changes in the components of the IGF system in individuals with established CVD or with increased CVD risk as with the metabolic syndrome? (2) What are the underlying mechanisms for interactions, if any, between insulin and the IGF system, in the genesis of CVD? (3) Can knowledge of the pathophysiological changes in the IGF system observed in macrosomic newborn infants and growth hormone (GH)-treated children and adults explain some of the observations in relation to the IGF system and the metabolic syndrome? (4) Can the experimental and clinical evidence adduced from the foregoing be useful in designing novel therapies for the prevention, treatment, and assignment of prognosis in metabolic syndrome-associated disease, particularly ischemic heart disease? To answer these questions, we have performed a literature review using bibliographies from PubMed, Medline, and Google Scholar published within the last 10 years. We suggest that IGF-1 levels are reduced consistently in individuals with the metabolic syndrome and its components and in those with ischemic CVD. Such changes are also seen with GH deficiency in which these changes are partially reversible with GH treatment. Furthermore, changes are seen in levels and interactions of IGF-binding proteins in these disorders, and some of these changes appear to be independent of IGF-binding capability and could potentially impact on risk for the metabolic syndrome and CVD. The promising therapeutic implications of these observations are also discussed.

Role for inducible cAMP early repressor in promoting pancreatic beta cell dysfunction evoked by oxidative stress in human and rat islets

AIMS/HYPOTHESIS

Pro-atherogenic and pro-oxidant, oxidised LDL trigger adverse effects on pancreatic beta cells, possibly contributing to diabetes progression. Because oxidised LDL diminish the expression of genes regulated by the inducible cAMP early repressor (ICER), we investigated the involvement of this transcription factor and of oxidative stress in beta cell failure elicited by oxidised LDL.

METHODS

Isolated human and rat islets, and insulin-secreting cells were cultured with human native or oxidised LDL or with hydrogen peroxide. The expression of genes was determined by quantitative real-time PCR and western blotting. Insulin secretion was monitored by EIA kit. Cell apoptosis was determined by scoring cells displaying pycnotic nuclei.

RESULTS

Exposure of beta cell lines and islets to oxidised LDL, but not to native LDL raised the abundance of ICER. Induction of this repressor by the modified LDL compromised the expression of important beta cell genes, including insulin and anti-apoptotic islet brain 1, as well as of genes coding for key components of the secretory machinery. This led to hampering of insulin production and secretion, and of cell survival. Silencing of this transcription factor by RNA interference restored the expression of its target genes and alleviated beta cell dysfunction and death triggered by oxidised LDL. Induction of ICER was stimulated by oxidative stress, whereas antioxidant treatment with N-acetylcysteine or HDL prevented the rise of ICER elicited by oxidised LDL and restored beta cell functions.

CONCLUSIONS/INTERPRETATION

Induction of ICER links oxidative stress to beta cell failure caused by oxidised LDL and can be effectively abrogated by antioxidant treatment.

Estrogens and selective estrogen receptor modulators regulate gene and protein expression in the mesenteric arteries

Estrogen has both beneficial and detrimental effects on the cardiovascular system. Selective estrogen receptor modulators (SERMs) exhibit partial estrogen agonist/antagonist activity in estrogen target tissues. Gene targets of estrogen and SERMs in the vasculature are not well-known. Thus, the present study tested the hypothesis that estrogens (ethinyl estradiol, estradiol benzoate, and equilin) and SERMs (tamoxifen and raloxifene) cause differential gene and protein expression in the vasculature. DNA microarray and real-time RT-PCR were used to investigate gene expression in the mesenteric arteries of estrogen and SERM treated ovariectomized rats. The genes shown to be differentially expressed included stearoyl-CoA desaturase (SCD), soluble epoxide hydrolase (sEH), secreted frizzled related protein-4 (SFRP-4), insulin-like growth factor-1 (IGF-1), phospholipase A2 group 1B (PLA2-G1B), and fatty acid synthase (FAS). Western blot further confirmed the differential expression of sEH, SFRP-4, FAS, and SCD protein. These results reveal that estrogens and SERMs cause differential gene and protein expression in the mesenteric artery. Consequently, the use of these agents may be associated with a unique profile of functional and structural changes in the mesenteric arterial circulation.

Thiazolidinediones up-regulate insulin-like growth factor-1 receptor via a peroxisome proliferator-activated receptor gamma-independent pathway

There is increasing evidence that thiazolidinediones (TZDs), antidiabetic compounds that are synthetic ligands for the peroxisome proliferator-activated receptor γ (PPARγ), have cardiovascular effects through as yet poorly defined mechanisms. We tested the effect of two TZD class drugs, rosiglitazone and pioglitazone, on human aortic smooth muscle cell (SMC) expression of insulin-like growth factor-1 receptor (IGF-1R). Both TZDs dose dependently up-regulated IGF-1R protein levels (rosiglitazone, 10 μmol/liter, 67% increase, n = 4, p < 0.01; pioglitazone, 10 μmol/liter, 41% increase, n = 4, p < 0.01) and increased IGF-1R signaling activity (36% increase in Akt phosphorylation). However, the endogenous PPARγ ligand, 15-deoxy-Δ(12,14)-prostaglandin J(2), dose dependently reduced IGF-1R (10 μmol/liter, 80% decrease, n = 4, p < 0.01), and overexpression of PPARγ using an adenovirus likewise reduced IGF-1R (50% decrease versus SMC infected with control adenovirus), suggesting a PPARγ-independent action of TZDs. All three PPARγ ligands (rosiglitazone, pioglitazone, and 15-deoxy-Δ(12,14)-prostaglandin J(2)), however, did not change IGF-1R mRNA levels, indicating that their effects were posttranscriptional. Use of bicistronic constructs revealed that TZD induction of IGF-1R translation occurred via internal ribosomal entry. To examine the potential physiological relevance of TZD up-regulation of IGF-1R, we determined the effect of rosiglitazone on oxidized LDL (oxLDL)-induced apoptosis. 20 μmol/liter of rosiglitazone reduced oxidized LDL-induced apoptosis by 40% and neutralizing antibody to IGF-1R (αIR3) counteracted this rescue, suggesting the rosiglitazone survival effect was, at least in part, mediated by IGF-1R. In conclusion, TZDs markedly up-regulate SMC IGF-1R expression and signaling, likely via a PPARγ-independent mechanism. This novel action of TZDs may play an important role in their cardiovascular effects.

Gene expression profiling identifies key estradiol targets in the frontal cortex of the rat

Estradiol modulates a wide range of neural functions in the frontal cerebral cortex where subsets of neurons express estrogen receptor-alpha and -beta. Through these receptors, estradiol contributes to the maintenance of normal operation of the frontal cortex. During the decline of gonadal hormones, the frequency of neurological and psychiatric disorders increases. To shed light on the etiology of disorders related to declining levels of estrogens, we studied the genomic responses to estradiol. Ovariectomized rats were treated with a sc injection of estradiol. Twenty-four hours later, samples from the frontal cortices were dissected, and their mRNA content was analyzed. One hundred thirty-six estradiol-regulated transcripts were identified on Rat 230 2.0 Expression Array. Of the 136 estrogen-regulated genes, 26 and 36 genes encoded proteins involved in the regulation of transcription and signal transduction, respectively. Thirteen genes were related to the calcium signaling pathway. They comprised five genes coding for neurotransmitter receptors. Transcription of three neuropeptides, including cocaine- and amphetamine-regulated transcript, were up-regulated. Fifty-two genes were selected for validation, and 12 transcriptional changes were confirmed. These results provided evidence that estradiol evokes broad transcriptional response in the cortex. Modulation of key components of the calcium signaling pathway, dopaminergic, serotonergic, and glutamatergic neurotransmission, may explain the influence of estrogens on cognitive function and behavior. Up-regulation of cocaine- and amphetamine-regulated transcript contributes to the neuroprotective effects of estradiol. Identification of estradiol-regulated genes in the frontal cortex helps to understand the pathomechanism of neurological and psychiatric disorders associated with altered levels of estrogens.

Age-related changes in redox signaling and VSMC function

Epidemiological studies have shown that advancing age is associated with an increased prevalence of cardiovascular disease (CVD). Vascular smooth muscle cells (VSMC) comprise the major arterial cell population, and changes in VSMC behavior, function, and redox status with age contribute to alterations in vascular remodeling and cell signaling. Over two decades of work on aged animal models provide support for age-related changes in VSMC and/or arterial tissues. Enhanced production of reactive oxygen species (ROS) and insufficient removal by scavenging systems are hallmarks of vascular aging. VSMC proliferation and migration are core processes in vascular remodeling and influenced by growth factors and signaling networks. The intrinsic link between gene regulation and aging often relates directly to transcription factors and their regulatory actions. Modulation of growth factor signaling leads to up- or downregulation of transcription factors that control expression of genes associated with VSMC proliferation, inflammation, and ROS production. Four major signaling pathways related to the transcription factors, AP-1, NF-kappaB, FoxO, and Nrf2, will be reviewed. Knowledge of age-related changes in signaling pathways in VSMC that lead to alterations in cell behavior and function consistent with disease progression may help in efforts to attenuate age-related CVD, such as atherosclerosis.

The insulin-like growth factor family: molecular mechanisms, redox regulation, and clinical implications

Insulin-like growth factor (IGF)-induced signaling networks are vital in modulating multiple fundamental cellular processes, such as cell growth, survival, proliferation, and differentiation. Aberrations in the generation or action of IGF have been suggested to play an important role in several pathological conditions, including metabolic disorders, neurodegenerative diseases, and multiple types of cancer. Yet the exact mechanism involved in the pathogenesis of these diseases by IGFs remains obscure. Redox pathways involving reactive oxygen species (ROS) and reactive nitrogen species (RNS) contribute to the pathogenetic mechanism of various diseases by modifying key signaling pathways involved in cell growth, proliferation, survival, and apoptosis. Furthermore, ROS and RNS have been demonstrated to alter IGF production and/or action, and vice versa, and thereby have the ability to modulate cellular functions, leading to clinical manifestations of diseases. In this review, we provide an overview on the IGF system and discuss the potential role of IGF-1/IGF-1 receptor and redox pathways in the pathophysiology of several diseases.

Age-related differences in insulin-like growth factor-1 receptor signaling regulates Akt/FOXO3a and ERK/Fos pathways in vascular smooth muscle cells

Advanced age is a major risk factor for atherosclerosis, but how aging per se influences pathogenesis is not clear. Insulin-like growth factor-1 receptor (IGF-1R) promotes aortic vascular smooth muscle cell (VSMC) growth, migration, and extracellular matrix formation, but how IGF-1R signaling changes with age in VSMC is not known. We previously found age-related differences in the activation of Akt/FOXO3a and ERK1/2 pathways in VSMC, but the upstream signaling remains unclear. Using explanted VSMC from Fischer 344/Brown Norway F1 hybrid rats shown to display age-related vascular pathology similar to humans, we compared IGF-1R expression in early passages of VSMC and found a constitutive activation of IGF-1R in VSMC from old compared to young rats, including IGF-1R expression and its tyrosine kinase activity. The link between IGF-1R activation and the Akt/FOXO3a and ERK pathways was confirmed through the induction of IGF-1R with IGF-1 in young cells and attenuation of IGF-1R with an inhibitor in old cells. The effects of three kinase inhibitors: AG1024, LY294002, and TCN, were compared in VSMC from old rats to differentiate IGF-1R from other upstream signaling that could also regulate the Akt/FOXO and ERK pathways. Genes for p27kip-1, catalase and MnSOD, which play important roles in the control of cell cycle arrest and stress resistance, were found to be FOXO3a-targets based on FOXO3a-siRNA treatment. Furthermore, IGF-1R signaling modulated these genes through activation of the Akt/FOXO3a pathway. Therefore, activation of IGF-1R signaling influences VSMC function in old rats and may contribute to the increased risk for atherosclerosis.

The role of IGF-I and its binding proteins in the development of type 2 diabetes and cardiovascular disease

Patients with insulin resistance and type 2 diabetes have an excessive risk of cardiovascular disease (CVD); this increased risk is not fully explained by traditional risk factors such as hypertension and dyslipidaemias. There is now compelling evidence to suggest that abnormalities of insulin-like growth factor-I (IGF-I) and one of its binding proteins, insulin-like growth factor-binding protein-1 (IGFBP-1), occur in insulin-resistant states and may be significant factors in the pathophysiology of CVD. We reviewed articles and relevant bibliographies following a systematic search of MEDLINE for English language articles between 1966 and the present, using an initial search strategy combining the MeSH terms: IGF, diabetes and CVD. Our aim was first to review the role of IGF-I in vascular homeostasis and to explore the mechanisms by which it may exert its effects. We also present an overview of the physiology of the IGF-binding proteins, and finally, we sought to summarize the evidence to date describing the changes in the insulin/IGF-I/IGFBP-1 axis that occur in type 2 diabetes and CVD; in particular, we have focused on the potential vasculoprotective effects of both IGF-I and IGFBP-1. We conclude that this system represents an interesting and novel therapeutic target in the prevention of CVD in type 2 diabetes.

Mechanism of the divergent effects of estrogen on the cell proliferation of human umbilical endothelial versus aortic smooth muscle cells

Diverse estrogen actions are controlled via estrogen receptors (ERs). Mechanisms of action of ERs are modulated by various factors such as ER subtypes, conformation of the ER-ligand complex, and recruitment of coregulator complexes to a target gene promoter. Estrogen exerts divergent actions on vascular cells; namely it increases endothelial cell and inhibits smooth muscle cell growth, resulting in a vasoprotective action. We particularly focused on these divergent effects and examined the mechanisms. The effects of raloxifene, which shows estrogen-like vasoprotective actions, were also examined. To examine the effects of 17beta-estradiol (E(2)) and raloxifene on human aortic smooth muscle cells (HASMCs) and human umbilical venous endothelial cells (HUVECs), we evaluated the effect of E(2) and raloxifene on transcriptional activity, recruitment of the coregulator complex to a target gene promoter, and acetylation of histone of both the IGF-I and COX-2 genes. Treatment with E(2) or raloxifene increased both IGF-I and cyclooxygenase (COX)-2 mRNA expression in HUVECs, whereas they attenuated the serum-induced increase of these genes in HASMCs. Treatment by E(2) and raloxifene induced recruitment of coactivator complex and histone acetylation at both the IGF-I and COX-2 gene promoter in HUVECs. In contrast, in HASMCs, E(2), and raloxifene attenuated the serum-induced recruitment of coactivator complexes and histone acetylation at both the IGF-I and COX-2 gene promoters. Estrogen and raloxifene exert divergent transcriptional regulation on both mRNA expression and the remodeling of IGF-I and COX-2 gene promoters in HUVECs vs. HASMCs.

Human high-density lipoprotein particles prevent activation of the JNK pathway induced by human oxidised low-density lipoprotein particles in pancreatic beta cells

AIMS/HYPOTHESIS

We explored the potential adverse effects of pro-atherogenic oxidised LDL-cholesterol particles on beta cell function.

MATERIALS AND METHODS

Isolated human and rat islets and different insulin-secreting cell lines were incubated with human oxidised LDL with or without HDL particles. The insulin level was monitored by ELISA, real-time PCR and a rat insulin promoter construct linked to luciferase gene reporter. Cell apoptosis was determined by scoring cells displaying pycnotic nuclei.

RESULTS

Prolonged incubation with human oxidised LDL particles led to a reduction in preproinsulin expression levels, whereas the insulin level was preserved in the presence of native LDL-cholesterol. The loss of insulin production occurred at the transcriptional levels and was associated with an increase in activator protein-1 transcriptional activity. The rise in activator protein-1 activity resulted from activation of c-Jun N-terminal kinases (JNK, now known as mitogen-activated protein kinase 8 [MAPK8]) due to a subsequent decrease in islet-brain 1 (IB1; now known as MAPK8 interacting protein 1) levels. Consistent with the pro-apoptotic role of the JNK pathway, oxidised LDL also induced a twofold increase in the rate of beta cell apoptosis. Treatment of the cells with JNK inhibitor peptides or HDL countered the effects mediated by oxidised LDL.

CONCLUSIONS/INTERPRETATION

These data provide strong evidence that oxidised LDL particles exert deleterious effects in the progression of beta cell failure in diabetes and that these effects can be countered by HDL particles.

Smoking induces glomerulosclerosis in aging estrogen-deficient mice through cross-talk between TGF-beta1 and IGF-I signaling pathways

Smoking is a known risk factor for the progression of chronic kidney diseases. However, its independent contribution to the development of ESRD and the underlying molecular mechanism have not been well elucidated. Although the risk for ESRD is higher in postmenopausal women according to the US Renal Data System, the number of women who smoke is on the rise worldwide. Therefore, the effects of smoking and estrogen status on glomerular function and structure were studied in female B6 mice that were ovariectomized at 3 (young) and 15 mo (aged) of age. The mice received either 17beta-estradiol (E(2)) replacement or placebo (Pla) and were divided further into groups that were exposed to cigarette smoke (S) and not exposed (NS). Six months of exposure to smoke had no effect on young mice, although aging S/Pla mice exhibited a phenotype of increased albumin excretion associated with a moderately increased glomerular collagen type IV deposition compared with NS/Pla mice. S/Pla mice also had a two-fold increase in glomerular TGF-beta, Smad3, and IGF-I receptor mRNA expression compared with the NS group. Mesangial cells that were isolated from S/Pla mice had an increase of IGF-I receptor protein, and IGF-I stimulated a TGF-beta reporter construct promoter three-fold. This was blocked by pretreatment with a neutralizing antibody to IGF-I, LY294002 (phosphatidylinositol-3 kinase inhibitor) or a dominant negative Smad construct. In addition, Smad3 activation was stimulated by IGF-I and blocked by LY294002, suggesting cross-talk between Smad and the phosphatidylinositol-3 kinase/AKT pathways. The smoking phenotype was reversed by E(2) replacement. In conclusion, smoking induces a phenotype in E(2)-deficient mice that is characterized by activation and cross-talk between the TGF-beta1 and IGF-I signaling pathways.

Acetaminophen recruits spinal p42/p44 MAPKs and GH/IGF-1 receptors to produce analgesia via the serotonergic system

The mechanism of action of acetaminophen is currently widely discussed. Direct inhibition of cyclooxygenase isoforms remains the commonly advanced hypothesis. We combined behavioral studies with molecular techniques to investigate the mechanism of action of acetaminophen in a model of tonic pain in rats. We show that acetaminophen indirectly stimulates spinal 5-hydroxytryptamine (5-HT)1A receptors in the formalin test, thereby increasing transcript and protein levels of low-affinity neurotrophin receptor, insulin-like growth factor-1 (IGF-1) receptor alpha subunit, and growth hormone receptor and reducing the amount of somatostatin 3 receptor (sst3R) mRNA. Those cellular events seem to be important for the antinociceptive activity of acetaminophen. Indeed, down-regulation of sst3R mRNA depends on acetaminophen-elicited, 5-HT1A receptor-dependent increase in neuronal extracellular signal-regulated kinase 1/2 (ERK1/2) activities that mediate antinociception. In addition, spinal growth hormone (GH) and IGF-1 receptors would also be involved in the antinociceptive activity of the analgesic at different degrees. Our results show the involvement of specific 5-HT1A receptor-dependent cellular events in acetaminophen-produced antinociception and consequently indicate that inhibition of cyclooxygenase activities is not the exclusive mechanism involved. Furthermore, we propose that the mechanisms of 5-HT1A receptor-elicited antinociception and the role of the spinal ERK1/2 pathway in nociception are more intricate than suspected so far and that the GH/IGF-1 axis is an interesting new player in the regulation of spinal nociception.

Hormonal regulation of hepatic IGF-I and IGF-II gene expression in the marine teleost Sparus aurata

The present work aimed to determine whether GnRH potentiates the effect of growth hormone (GH) on insulin-like growth factors (IGF-I and IGF-II) hepatic gene expression in Sparus aurata liver. Since several hepatic genes were shown to underlie direct regulation via the hepatic estrogen receptor, another aim was to extend our understanding of direct estrogen effects on liver IGFs gene expression. Pre-reproductive sea bream females were treated with GH, GnRH, estradiol-17beta, GH plus GnRH, and estradiol-17beta plus GH. After 72 hr, all treatment induced an increase of plasma estradiol well correlated with the increase of plasma vitellogenin (VTG) levels. IGF-I and IGF-II expression in the liver of treated females was determined by semi-quantitative RT-PCR, using beta-actin as internal standard. The results reported here show that GH significantly stimulates hepatic transcription of IGF-I and IGF-II genes. Surprisingly, E2 and GnRH treatments decreased both IGF-I and IGF-II mRNA levels. In fishes treated with GH plus GnRH, the GnRH contrasted the GH effect: the IGF-I mRNA levels were still significantly higher than in controls, while the effect of GH on IGF-II gene expression was totally abolished. At the same time, in the combined treatment with GH plus E2, the E2 counteracted the stimulatory effect of GH on both IGF-I and IGF-II genes expression.

Induction of apolipoprotein E expression by TR4 orphan nuclear receptor via 5′ proximal promoter region

While other plasma lipoproteins are exclusively expressed in liver and intestine, apoliprotein E (apoE) is ubiquitously synthesized in many tissues. To understand the molecular mechanism of non-tissue-specific apoE expression, we tested the testicular orphan receptor 4 (TR4) effect on apoE expression in different cell lines, such as HepG2, COS-1, and H1299 cells. Gel shift assay and 5' promoter activity analyses identified one distinct hormone response element (TR4RE-DR0-apoE at -303 to -292 bp) that binds to TR4 and results in full induction of apoE gene transcription. TR4 also forms a complex with Sp1 to synergistically induce apoE expression via a region containing the TR4RE-DR0-apoE and the Sp1 binding site (-169 to -140 bp). Induction of apoE expression by TR4 was also confirmed at the mRNA and protein levels in H1299 cells. Together, our data demonstrate that TR4 can enhance apoE gene expression via binding to TR4RE-DR0 in apoE 5' promoter and this TR4 binding is essential for synergistic interaction with another transcription factor, Sp1.

Autocrine activation of the local insulin-like growth factor I system is up-regulated by estrogen receptor (ER)-independent estrogen actions and accounts for decreased ER expression in type 2 diabetic mesangial cells

Autocrine activation of the IGF-I system in mesangial cells (MC) promotes glomerular scarring in a model of type 1 diabetes. Although estrogens protect against progressive nondiabetic glomerulosclerosis (GS), women with diabetes seem to loose the estrogen-mediated protection against cardiovascular disease. However, little is known about the local IGF-I system and its interactions with estrogens in the pathogenesis of type 2 diabetic GS. Therefore, we examined db/db B6 (db/db) mice, a model of type 2 diabetes and diabetic GS. The IGF-I system was activated in the glomeruli and MC of female diabetic db/db mice, but not in nondiabetic db/+ littermates. We found increased IGF-I receptor (IGFR) expression and activation, including activation of MAPK. Surprisingly, estrogens, via an estrogen receptor (ER)-independent mechanism(s), increased IGFR expression, IGFR and insulin receptor substrate phosphorylation, and extracellular signal-regulated kinase activation in db/db MC. In contrast, ER expression was decreased in MC and glomeruli of db/db mice. Treatment with a neutralizing antibody to IGF-I or the MAPK inhibitor PD98059 increased ER expression and transcriptional activity. This suggests that the local prosclerotic IGF-I system is activated in type 2 diabetes and diminishes ER-mediated protection against GS. Although estrogens may stimulate protective ER signaling, they also activate the IGF-I system via ER-independent mechanisms in db/db MC. The later estrogen effects appear to outweigh the antisclerotic effects of ER activation. This may in part account for loss of estrogen protection against the progression of diabetic GS in women with type 2 diabetes.

Cell type-specific bidirectional regulation of the glucocorticoid-induced leucine zipper (GILZ) gene by estrogen

Estrogen has numerous beneficial physiological actions; however, by acting as a mitogen, it plays a significant role in the induction and maintenance of breast cancer. Although the positive effects of estrogen on gene expression are well described, negative gene regulation is not. Using microarray analysis, we identified 27 genes that were up-regulated and 20 that were down-regulated by estrogen in MCF-7 human breast cancer cells. One gene encoding GILZ (glucocorticoid-induced leucine zipper protein), a putative apoptosis-regulating transcription factor, is rapidly down-regulated by estrogen in these cells. Estrogen antagonists block the down-regulation. The region of the GILZ promoter between nucleotides -104 and -69 mediates both basal activity and estrogen-dependent down-regulation in MCF-7 cells. This region contains a functional Oct-1 binding site and a cyclic AMP response element binding protein (CREB) binding site. The same DNA region mediates up-regulation by estrogen in HeLa and HEK293 cells, indicating that cell-specific factors are involved in estrogen regulation of this gene. The estrogen receptor (ER) is present in GILZ promoter protein complexes, but it does not bind directly to the promoter itself, as the DNA-binding domain of the estrogen receptor is not required for down-regulation. Elimination of the CREB binding site blocks both basal activity and estrogen regulation. Our results suggest that ER action at the CRE may mediate estrogen-dependent, cell-specific regulation of this gene.

The extracellular matrix, p53 and estrogen compete to regulate cell-surface Fas/Apo-1 suicide receptor expression in proliferating embryonic cerebral cortical precursors, and reciprocally, Fas-ligand modifies estrogen control of cell-cycle proteins

BACKGROUND

Apoptosis is important for normal cerebral cortical development. We previously showed that the Fas suicide receptor was expressed within the developing cerebral cortex, and that in vitro Fas activation resulted in caspase-dependent death. Alterations in cell-surface Fas expression may significantly influence cortical development. Therefore, in the following studies, we sought to identify developmentally relevant cell biological processes that regulate cell-surface Fas expression and reciprocal consequences of Fas receptor activation.

RESULTS

Flow-cytometric analyses identified two distinct neural sub-populations that expressed Fas on their cell surface at high (FasHi) or moderate (FasMod) levels. The anti-apoptotic protein FLIP further delineated a subset of Fas-expressing cells with potential apoptosis-resistance. FasMod precursors were mainly in G0, while FasHi precursors were largely apoptotic. However, birth-date analysis indicated that neuroblasts express the highest levels of cell-surface Fas at the end of S-phase, or after their final round of mitosis, suggesting that Fas expression is induced at cell cycle checkpoints or during interkinetic nuclear movements. FasHi expression was associated with loss of cell-matrix adhesion and anoikis. Activation of the transcription factor p53 was associated with induction of Fas expression, while the gonadal hormone estrogen antagonistically suppressed cell-surface Fas expression. Estrogen also induced entry into S-phase and decreased the number of Fas-expressing neuroblasts that were apoptotic. Concurrent exposure to estrogen and to soluble Fas-ligand (sFasL) suppressed p21/waf-1 and PCNA. In contrast, estrogen and sFasL, individually and together, induced cyclin-A expression, suggesting activation of compensatory survival mechanisms.

CONCLUSIONS

Embryonic cortical neuronal precursors are intrinsically heterogeneous with respect to Fas suicide-sensitivity. Competing intrinsic (p53, cell cycle, FLIP expression), proximal (extra-cellular matrix) and extrinsic factors (gonadal hormones) collectively regulate Fas suicide-sensitivity either during neurogenesis, or possibly during neuronal migration, and may ultimately determine which neuroblasts successfully contribute neurons to the differentiating cortical plate.

Estrogen regulation of vascular endothelial growth factor gene expression in ZR-75 breast cancer cells through interaction of estrogen receptor alpha and SP proteins

Vascular endothelial growth factor (VEGF) is expressed in multiple hormone-dependent cancer cells/tumors. Treatment of ZR-75 breast cancer cells with 17beta-estradiol (E2) induced a greater than fourfold increase of VEGF mRNA levels. ZR-75 breast cancer cells were transfected with pVEGF1, a construct containing a -2018 to +50 VEGF promoter insert, and E2 induced reporter gene (luciferase) activity. Deletion and mutation analysis of the VEGF gene promoter identified a GC-rich region (-66 to -47) which was required for E2-induced transactivation of pVEGF5, a construct containing the minimal promoter (-66 to +54) that exhibited E2-responsiveness. Interactions of nuclear proteins from ZR-75 cells with the proximal GC-rich region of the VEGF gene promoter were investigated by electrophoretic mobility shift and chromatin immunoprecipitation assays. The results demonstrate that both Sp1 and Sp3 proteins bound the GC-rich motif (-66 to -47), and estrogen receptor alpha (ERalpha) interactions were confirmed by chromatin immunoprecipitation. Moreover, E2-dependent activation of constructs containing proximal and distal GC/GT-rich regions of the VEGF promoter was inhibited in ZR-75 cells transfected with small inhibitory RNAs for Sp1 and Sp3. These results were consistent with a mechanism of hormone activation of VEGF through ERalpha/Sp1 and ERalpha/Sp3 interactions with GC-rich motifs.

An activator protein 1-like motif mediates 17beta-estradiol repression of gonadotropin-releasing hormone receptor promoter via an estrogen receptor alpha-dependent mechanism in ovarian and breast cancer cells

Although it is recognized that estrogen is one of the most important regulators of GnRH receptor (GnRHR) gene expression, the mechanism underlying the regulation at the transcriptional level is unknown. In the present study, we demonstrated that 17beta-estradiol (E2) repressed human GnRHR promoter via an activator protein 1-like motif and estrogen receptor-alpha, of which the DNA-binding domain and the ligand-binding domain were indispensable for the repression. Interestingly, the same cis-acting motif was also found to be important for both the basal activity and phorbol 12-myristate 13-acetate responsiveness of the GnRHR promoter. EMSAs indicated that multiple transcription factors including c-Jun and c-Fos bound to the activator protein 1-like site and that their DNA binding activity was not significantly affected by E2 treatment. In addition, we demonstrated that the E2 repression could be antagonized by phorbol 12-myristate 13-acetate, which stimulated c-Jun phosphorylation on serine 63, a process that is a prerequisite for recruitment of the transcriptional coactivator cAMP response element binding protein (CREB)-binding protein (CBP). Concomitantly, we found that overexpression of CBP could reverse the suppression in a dose-dependent manner. Taken together, our data indicate that E2-activated estrogen receptor-alpha represses human GnRHR gene transcription via an indirect mechanism involving CBP and possibly other transcriptional regulators.

Expression, regulation, and function of IGF-1, IGF-1R, and IGF-1 binding proteins in blood vessels

The vascular insulin-like growth factor (IGF)-1 system includes the IGFs, the IGF-1 receptor (IGF-1R), and multiple binding proteins. This growth factor system exerts multiple physiologic effects on the vasculature through both endocrine and autocrine/paracrine mechanisms. The effects of IGF-1 are mediated principally through the IGF-1R but are modulated by complex interactions with multiple IGF binding proteins that themselves are regulated by phosphorylation, proteolysis, polymerization, and cell or matrix association. During the last decade, a significant body of evidence has accumulated, indicating that expression of the components of the IGF system are regulated by multiple factors, including growth factors, cytokines, lipoproteins, reactive oxygen species, and hemodynamic forces. In addition, cross-talk between the IGF system and other growth factors and integrin receptors has been demonstrated. There is accumulating evidence of a role for IGF-1 in multiple vascular pathologies, including atherosclerosis, hypertension, restenosis, angiogenesis, and diabetic vascular disease. This review will discuss the regulation of expression of IGF-1, IGF-1R, and IGF binding proteins in the vasculature and summarize evidence implicating involvement of this system in vascular diseases.

What pharmacologists can learn from recent advances in estrogen signalling

The discovery of the second estrogen receptor (ER) in 1995 surprised many endocrinologists and resulted in some scepticism regarding its physiological importance. However, 8 years later, it is clear that the multiple actions of estrogen in the body are mediated by two receptors that, although similar, are distinct gene products with non-overlapping functions. This clear delineation of the functions of the two receptors in such a short time was made possible by the development of ER alpha and ER beta knockout mice. The distinct patterns of tissue distribution of these two receptors has heightened interest in novel estrogen targets in the body and has led to awareness of new sites for pharmacological intervention in diseases such as depression, prostate dysfunction, leukaemia, inflammatory bowel disease and colon cancer.

BRCA1-Sp1 interactions in transcriptional regulation of the IGF-IR gene

The insulin-like growth factor-I receptor (IGF-IR) plays a critical role in breast tumorigenesis and is overexpressed in most primary tumors. BRCA1 is a transcription factor involved in numerous cellular processes, including DNA damage repair, cell growth, and apoptosis. Consistent with its tumor suppressor role, we demonstrated that BRCA1 repressed the activity of co-transfected IGF-IR promoter reporter constructs in a number of breast cancer-derived cell lines. Results of electrophoretic mobility shift assay showed that BRCA1 did not exhibit any specific binding to the IGF-IR promoter, although it prevented binding of Sp1. Co-immunoprecipitation experiments demonstrated that BRCA1 action was associated with specific interaction with Sp1 protein. Furthermore, using a series of glutathione S-transferase-tagged BRCA1 fragments, we mapped the Sp1-binding domain to a segment located between aa 260 and 802. In summary, our data suggest that the IGF-IR gene is a novel downstream target for BRCA1 action.

Estroprogestinic pill normalizes IGF-I levels in acromegalic women

In some acromegalic patients medical treatment does not succeed in normalizing GH/IGF-I values. Data showing IGF-I suppression in acromegaly by estrogen and by tamoxifen use prompted us to reevaluate the effects of estroprogestins (EP) supplementation on GH/IGF-I levels in acromegalic women resistant or only partially sensitive to medical treatment. Eight active acromegalic women (30-52 yr, 4 with regular menses) entered a prospective open pilot study. Three of them, resistant to medical treatment, were off therapy; the remaining five, partially sensitive, maintained it at the maximally effective dosages throughout the study. Patients were treated with a triphasic pill (ethynil-estradiol 30-40-30 microg/day and desogestrel 50-70-100 mg/day) for 13 +/- 7 months. IGF-I levels fell from 512 (median, interquartile 436-657) microg/l to 282 (244-526) microg/l (p=0.0414); the decrease was observed in 6 patients (75%), and normal values were reached in 4 (50%). GH levels did not change [basal 7.6 (6.2-8.6) microg/l, final 7.6 (6.5-8.3) microg/l]. Effectiveness of treatment was not dependent on concomitant anti-GH treatment or gonadal status. In all patients IGF-I levels re-increased after EP withdrawal. This pilot study shows a marked IGF-I lowering effect of pill in acromegalic women, and warrants a prospective randomized study in patients resistant or partially sensitive to other medical treatments.

Transcriptional regulation of the mouse fatty acid amide hydrolase gene

Fatty acid amide hydrolase (FAAH) is a membrane-bound enzyme that inactivates a family of fatty acid amide molecules which are implicated in physiological processes such as pain and sleep. We cloned a 1.9 kb fragment of the 5'-untranslated region of the mouse FAAH gene into the pGL3 basic luciferase reporter vector and showed that this sequence has promoter activity in vitro. By primer extension analysis, we have determined the transcription start site to be 200 bases upstream of the ATG initiation codon and found that a TATA motif was absent. A number of putative response elements, including those for estrogen and glucocorticoids, were identified in this sequence. We have demonstrated that the estrogen and glucocorticoid receptors down-regulate transcriptional activity independent of their ligand. These data should help in understanding the mechanisms of FAAH gene transcription.

The PGC-1-related protein PERC is a selective coactivator of estrogen receptor alpha

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) is a tissue-specific coactivator that enhances the activity of many nuclear receptors and coordinates transcriptional programs important for energy metabolism. We describe here a novel PGC-1-related coactivator that is expressed in a similar tissue-specific manner as PGC-1, with the highest levels in heart and skeletal muscle. In contrast to PGC-1, the new coactivator shows high receptor specificity. It enhances potently the activity of estrogen receptor (ER) alpha, while having only small effects on other receptors. Because of its nuclear receptor selectivity, we have termed the new protein PERC (PGC-1 related Estrogen Receptor Coactivator). We show here that the coactivation function of PERC relies on a bipartite transcriptional activation domain and two LXXLL motifs that interact with the AF2 domain of ERalpha in an estrogen-dependent manner. PERC and PGC-1 are likely to have different functions in ER signaling. Whereas PERC acts selectively on ERalpha and not on the second estrogen receptor ERbeta, PGC-1 coactivates strongly both ERs. Moreover, PERC and PGC-1 show distinct preferences for enhancing ERalpha in different promoter contexts. Finally, PERC enhances the ERalpha-mediated response to the partial agonist tamoxifen, while PGC-1 modestly represses it. The two coactivators are likely to mediate distinct, tissue-specific responses to estrogens.

Effects of synthetic progestagens on the mRNA expression of androgen receptor, progesterone receptor, oestrogen receptor alpha and beta, insulin-like growth factor-1 (IGF-1) and IGF-1 receptor in heifer tissues

Synthetic progestagens like melengestrol acetate (MGA) are widely used for oestrus synchronization and for growth promotion in cattle production. The metabolic effects exceed its primary potency as a progestagen. It is speculated that MGA stimulates follicle development and thereby endogenous oestrogen production, but inhibits ovulation. To investigate the dose-dependent effects on mRNA expression levels, six heifers were fed for 8 weeks with different levels of MGA (0.5, 1.5, 5 mg) daily and two heifers served as controls. The expression of steroid receptor mRNA [androgen receptor (AR), progesterone receptor (PR), oestrogen receptor (ER) ERalpha and ERbeta], insulin-like growth factor-1 (IGF-1) and its receptor were quantified in liver, neck (m. splenius) and shoulder muscularity (m. deltoideus). Plasma concentrations of IGF-1 were quantified by radioimmunoassay. In treated animals the MGA plasma levels were elevated over the complete treatment period, corresponding to the MGA treatment concentrations. IGF-1 concentrations of control animals were at constant levels. Plasma levels for oestradiol (E2) and IGF-1 were increased in the low MGA treatment group. Overdosed MGA decreased progesterone (P4) and E2 levels. To quantify the IGF-1 and all receptor mRNA transcripts, sensitive and reliable real-time reverse transcription-polymerase chain reaction (RT-PCR) quantification methods were developed and validated in the LightCycler. A dose-dependent relationship between increasing MGA concentration and mRNA expression was observed in liver for AR and IGF-1 receptor, and in neck muscularity for IGF-1. ERalpha in liver and neck muscle showed a trend of increasing expression.

Selected contribution: estrogen receptor-alpha gene transfer inhibits proliferation and NF-kappaB activation in VSM cells from female rats

Epidemiological studies have demonstrated that hormone replacement therapy with estrogen (E2) or E2 plus progesterone in postmenopausal women decreases the age-associated risk of cardiovascular disease by 30-50%. Treatment of vascular smooth muscle (VSM) cells with physiological concentrations of E2 has been shown to inhibit growth factor-stimulated cell proliferation. In this study, we tested the hypothesis that E2 inhibits the age-associated increase in VSM cell proliferation by inhibiting nuclear factor (NF)-kappaB pathway. We investigated the effects of E2 treatment and adenovirus-mediated estrogen receptor (ER)-alpha gene transfer on cell proliferation and NF-kappaB activation using VSM cells cultured from 3-mo-old and 24-mo-old Fischer 344 female rats. Our results demonstrate that VSM cell proliferation was significantly increased (P < 0.05) in aged compared with young adult female rats. Treatment of VSM cells with physiological concentrations of E2 inhibited VSM cell proliferation, and this inhibition was significantly greater (P < 0.05) in cells from aged female rats compared with young adults. The inhibitory effects of E(2) on cell proliferation in aged female rats were significantly potentiated by overexpression of the human ER-alpha gene into VSM cells. Constitutive and interleukin (IL)-1beta-stimulated NF-kappaB activation was significantly greater (P < 0.05) in VSM cells from aged compared with young female rats. E2 treatment of VSM cells from aged female rats inhibited both constitutive and IL-1beta-stimulated NF-kappaB activation. ER-alpha gene transfer into VSM cells from aged female rats further augmented the inhibitory effects of E2. In conclusion, our data demonstrate that constitutive and IL-1beta-stimulated NF-kappaB activation is increased in VSM cells from aged female rats due to loss of E2 and this can be restored back to normal levels by ER-alpha gene transfer and E2 treatment. In addition, increased NF-kappaB signaling may be responsible for increased incidence of cardiovascular disease in postmenopausal females.

Apoptosis in atherosclerosis: focus on oxidized lipids and inflammation

An increasing body of evidence from both animal models and human specimens suggests that apoptosis or programmed cell death is a major event in the pathophysiology of atherosclerosis. Although the significance of apoptosis in atherosclerosis remains unclear, it has been proposed that apoptotic cell death contributes to plaque instability, rupture and thrombus formation. Biochemical and genetic analyses of apoptosis provide an increasingly detailed picture of the intracellular signaling pathways involved. Nevertheless, it remains to be determined whether apoptosis can become a clinically important approach to modulate plaque progression. In this review, we have outlined some of the most recent results concerning apoptosis in atherosclerosis with a special focus on oxidized lipids, inflammation and therapeutic regulation of the apoptotic cell death process.