Dexamethasone-induced and estradiol-induced CREB activation and annexin 1 expression in CCRF-CEM lymphoblastic cells: evidence for the involvement of cAMP and p38 MAPK

An overview of the regulatory role of annexin A1 in the tumor microenvironment and its prospective clinical application (Review)

Although annexin A1 (ANXA1), a 37 kDa phospholipid‑binding anti‑inflammatory protein expressed in various tissues and cell types, has been investigated extensively for its regulatory role in cancer biology, studies have mainly focused on its intracellular role. However, cancer cells and stromal cells expressing ANXA1 have the ability to transmit signals within the tumor microenvironment (TME) through autocrine, juxtacrine, or paracrine signaling. This bidirectional crosstalk between cancer cells and their environment is also crucial for cancer progression, contributing to uncontrolled tumor proliferation, invasion, metastasis and resistance to therapy. The present review explored the important role of ANXA1 in regulating the cell‑specific crosstalk between various compartments of the TME and analyzed the guiding significance of the crosstalk effects in promotion or suppressing cancer progression in the development of cancer treatments. The literature shows that ANXA1 is critical for the regulation of the TME, indicating that ANXA1 signaling between cancer cells and the TME is a potential therapeutic target for the development of novel therapeutic approaches for impeding cancer development.

Gene Expression and Resistance to Glucocorticoid-Induced Apoptosis in Acute Lymphoblastic Leukemia: A Brief Review and Update

BACKGROUND

Resistance to glucocorticoid (GC)-induced apoptosis in Acute Lymphoblastic Leukemia (ALL), is considered one of the major prognostic factors for the disease. Prednisolone is a corticosteroid and one of the most important agents in the treatment of acute lymphoblastic leukemia. The mechanics of GC resistance are largely unknown and intense ongoing research focuses on this topic.

AIM

The aim of the present study is to review some aspects of GC resistance in ALL, and in particular of Prednisolone, with emphasis on previous and present knowledge on gene expression and signaling pathways playing a role in the phenomenon.

METHODS

An electronic literature search was conducted by the authors from 1994 to June 2019. Original articles and systematic reviews selected, and the titles and abstracts of papers screened to determine whether they met the eligibility criteria, and full texts of the selected articles were retrieved.

RESULTS

Identification of gene targets responsible for glucocorticoid resistance may allow discovery of drugs, which in combination with glucocorticoids may increase the effectiveness of anti-leukemia therapies. The inherent plasticity of clinically evolving cancer justifies approaches to characterize and prevent undesirable activation of early oncogenic pathways.

CONCLUSION

Study of the pattern of intracellular signal pathway activation by anticancer drugs can lead to development of efficient treatment strategies by reducing detrimental secondary effects.

Anti-Inflammatory Drugs as Anticancer Agents

Inflammation is strictly associated with cancer and plays a key role in tumor development and progression. Several epidemiological studies have demonstrated that inflammation can predispose to tumors, therefore targeting inflammation and the molecules involved in the inflammatory process could represent a good strategy for cancer prevention and therapy. In the past, several clinical studies have demonstrated that many anti-inflammatory agents, including non-steroidal anti-inflammatory drugs (NSAIDs), are able to interfere with the tumor microenvironment by reducing cell migration and increasing apoptosis and chemo-sensitivity. This review focuses on the link between inflammation and cancer by describing the anti-inflammatory agents used in cancer therapy, and their mechanisms of action, emphasizing the use of novel anti-inflammatory agents with significant anticancer activity.

Evaluation of phytoestrogens in inducing cell death mediated by decreasing Annexin A1 in Annexin A1-knockdown leukemia cells

BACKGROUND

Phytoestrogens are plant compounds that are structurally similar to estrogen and that possess anti-cancer properties. Previous studies have reported that coumestrol, daidzein and genistein could induce cell death by reducing Annexin A1 protein in leukemic cell lines. Annexin A1 (ANXA1) is involved in cell progression, metastasis, and apoptosis in several types of cancer cells. The present study sought to investigate if the effects of phytoestrogens on apoptosis, cell cycle arrest and phagocytosis in ANXA1-knockdown leukemic cells are mediated through ANXA1 or occurred independently.

METHODS

Transfection of ANXA1 siRNA was conducted to downregulate ANXA1 expression in Jurkat, K562 and U937 cells. Apoptosis and cell cycle assays were conducted using flow cytometry. Western blot was performed to evaluate ANXA1, caspases and Bcl-2 proteins expression. Phagocytosis was determined using hematoxylin and eosin staining.

RESULTS

The expression of ANXA1 after the knockdown was significantly downregulated in all cell lines. Genistein significantly induced apoptosis associated with an upregulation of procaspase-3, -9, and - 1 in Jurkat cells. The Bcl-2 expression showed no significant difference in Jurkat, K562 and U937 cells. Treatment with phytoestrogens increased procaspase-1 expression in Jurkat and U937 cells while no changes were detected in K562 cells. Flow cytometry analysis demonstrated that after ANXA1 knockdown, coumestrol and genistein caused cell cycle arrest at G2/M phase in selected type of cells. The percentage of phagocytosis and phagocytosis index increased after the treatment with phytoestrogens in all cell lines.

CONCLUSION

Phytoestrogens induced cell death in ANXA1-knockdown leukemia cells, mediated by Annexin A1 proteins. Graphical abstract.

Neurotoxic effects of MPTP on mouse cerebral cortex: Modulation of neuroinflammation as a neuroprotective strategy

Parkinson's disease (PD) is a progressive neurological disorder, mainly characterized by the progressive loss of dopaminergic neurons in the Substantia nigra pars compacta (SNpc) and by the presence of intracellular inclusions, known as Lewy bodies. Despite SNpc being considered the primary affected region in PD, the neuropathological features are confined solely to the nigro-striatal axis. With disease progression other brain regions are also affected, namely the cerebral cortex, although the spreading of the neurologic damage to this region is still not completely unraveled. Tauroursodeoxycholic acid (TUDCA) is an endogenous bile acid that has been shown to have antioxidant properties and to exhibit a neuroprotective effect in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mice model of PD. Moreover, TUDCA anti-inflammatory properties have been reported in glial cells, making it a prominent therapeutic agent in PD. Here, we used C57BL/6 mice injected with MPTP in a sub-acute paradigm aiming to investigate if the neurotoxic effects of MPTP could be extended to the cerebral cortex. In parallel, we evaluated the anti-oxidant, neuroprotective and anti-inflammatory effects of TUDCA. The anti-inflammatory mechanisms elicited by TUDCA were further dissected in microglia cells. Our results show that MPTP leads to a decrease of ATP and activated AMP-activated protein kinase levels in mice cortex, and to a transient increase in the expression of antioxidant downstream targets of nuclear factor erythroid 2 related factor 2 (Nrf-2), and parkin. Notably, MPTP increases pro-inflammatory markers, while down-regulating the expression of the anti-inflammatory protein Annexin-A1 (ANXA1). Importantly, we show that TUDCA treatment prevents the deleterious effects of MPTP, sustains increased levels of antioxidant enzymes and parkin, and most of all negatively modulates neuroinflammation and up-regulates ANXA1 expression. Additionally, results from cellular models using microglia corroborate TUDCA modulation of ANXA1 synthesis, linking inhibition of neuroinflammation and neuroprotection by TUDCA.

The resolution of acute inflammation induced by cyclic AMP is dependent on annexin A1

Annexin A1 (AnxA1) is a glucocorticoid-regulated protein known for its anti-inflammatory and pro-resolving effects. We have shown previously that the cAMP-enhancing compounds rolipram (ROL; a PDE4 inhibitor) and Bt₂cAMP (a cAMP mimetic) drive caspase-dependent resolution of neutrophilic inflammation. In this follow-up study, we investigated whether AnxA1 could be involved in the pro-resolving properties of these compounds using a model of LPS-induced inflammation in BALB/c mice. The treatment with ROL or Bt₂cAMP at the peak of inflammation shortened resolution intervals, improved resolution indices, and increased AnxA1 expression. In vitro studies showed that ROL and Bt₂cAMP induced AnxA1 expression and phosphorylation, and this effect was prevented by PKA inhibitors, suggesting the involvement of PKA in ROL-induced AnxA1 expression. Akin to these in vitro findings, H89 prevented ROL- and Bt₂cAMP-induced resolution of inflammation, and it was associated with decreased levels of intact AnxA1. Moreover, two different strategies to block the AnxA1 pathway (by using N-t-Boc-Met-Leu-Phe, a nonselective AnxA1 receptor antagonist, or by using an anti-AnxA1 neutralizing antiserum) prevented ROL- and Bt₂cAMP-induced resolution and neutrophil apoptosis. Likewise, the ability of ROL or Bt₂cAMP to induce neutrophil apoptosis was impaired in AnxA-knock-out mice. Finally, in in vitro settings, ROL and Bt₂cAMP overrode the survival-inducing effect of LPS in human neutrophils in an AnxA1-dependent manner. Our results show that AnxA1 is at least one of the endogenous determinants mediating the pro-resolving properties of cAMP-elevating agents and cAMP-mimetic drugs.

Interaction between ANXA1 and GATA-3 in Immunosuppression of CD4+ T Cells

Decreased Th1/Th2 ratio is one of the major characteristics of immunosuppression in sepsis. Both membrane adhesive protein Annexin-A1 (ANXA1) and transcription factor GATA-3 have been reported to play important roles in T cell differentiation. However, the relationship between ANXA1 and GATA-3 in Th1/Th2 shift is unknown. Our study investigated the interaction effects of ANXA1 and GATA-3 to influence T cell differentiation in CD4+ T cells. We found that GATA-3 and ANXA1 were coexpressed on Th0/Th1/Th2 cytoplasm and nuclear. Overexpressed ANXA1 significantly increased the expression of IFNγ and reduced IL-4 expression in T cells, while ANXA1-silenced T cells exhibited decreased production of IFNγ and increased production of IL-4. Knockdown of ANXA1 promoted higher expression level of GATA-3 and low level of T-box transcription factor (T-bet/Tbx21). Further study demonstrated that ANXA1 regulated GATA-3 expression through the formyl peptide receptor like-1 (FPRL-1) downstream signaling pathways ERK and PKB/Akt. These results suggested that ANXA1 modulates GATA-3/T-bet expression induced Th0/Th1 differentiation. Moreover, we found that GATA-3 inhibited ANXA1 expression by binding to its promoter for the first time. It is proposed that the interactions between ANXA1 and GATA-3 may provide clues to understand the immunosuppression and have potential as new therapeutic targets in immunotherapy after sepsis.

Imprinting of Skin/Inflammation Homing in CD4+ T Cells Is Controlled by DNA Methylation within the Fucosyltransferase 7 Gene

E- and P-selectin ligands (E- and P-ligs) guide effector memory T cells into skin and inflamed regions, mediate the inflammatory recruitment of leukocytes, and contribute to the localization of hematopoietic precursor cells. A better understanding of their molecular regulation is therefore of significant interest with regard to therapeutic approaches targeting these pathways. In this study, we examined the transcriptional regulation of fucosyltransferase 7 (FUT7), an enzyme crucial for generation of the glycosylated E- and P-ligs. We found that high expression of the coding gene fut7 in murine CD4⁺ T cells correlates with DNA demethylation within a minimal promoter in skin/inflammation-seeking effector memory T cells. Retinoic acid, a known inducer of the gut-homing phenotype, abrogated the activation-induced demethylation of this region, which contains a cAMP responsive element. Methylation of the promoter or mutation of the cAMP responsive element abolished promoter activity and the binding of CREB, confirming the importance of this region and of its demethylation for fut7 transcription in T cells. Furthermore, studies on human CD4⁺ effector memory T cells confirmed demethylation within FUT7 corresponding to high FUT7 expression. Monocytes showed an even more extensive demethylation of the FUT7 gene whereas hepatocytes, which lack selectin ligand expression, exhibited extensive methylation. In conclusion, we show that DNA demethylation within the fut7 gene controls selectin ligand expression in mice and humans, including the inducible topographic commitment of T cells for skin and inflamed sites.

Role of 3'-5'-cyclic adenosine monophosphate on the epidermal growth factor dependent survival in mammary epithelial cells

Epidermal growth factor (EGF) has been suggested to play a key role in the maintenance of epithelial cell survival during lactation. Previously, we demonstrated that EGF dependent activation of PI3K pathway prevents apoptosis in confluent murine HC11 cells cultured under low nutrient conditions. The EGF protective effect is associated with increased levels of the antiapoptotic protein Bcl-XL. Here, we identify the EGF-dependent mechanism involved in cell survival that converges in the regulation of bcl-X expression by activated CREB. EGF induces Bcl-XL expression through activation of a unique bcl-X promoter, the P1; being not only the PI3K/AKT signaling pathway but also the increase in cAMP levels and the concomitant PKA/CREB activation necessary for both bcl-XL upregulation and apoptosis avoidance. Results presented in this work suggest the existence of a novel connection between the EGF receptor and the adenylate cyclase that would have an impact in preventing apoptosis under low nutrient conditions.

Downregulation of Annexin A1 by short hairpin RNA inhibits the osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells

Annexin A1 (ANX A1) is essential in cell differentiation and proliferation. However, the role of ANX A1 in bone marrow-derived mesenchymal stem cell (BM-MSC) osteogenic differentiation and proliferation remains unclear. To investigate whether endogenous ANX A1 influences BM-MSC proliferation and osteogenic differentiation, a stable ANX A1-knockdown cell line was generated using short hairpin RNA (shRNA). The proliferation rate of BM-MSCs was analyzed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide proliferation assay. Additionally, BM-MSCs were differentiated into osteoblasts and subsequently used to isolate total proteins to analyze the expression of ANX A1. Cell differentiation was assayed using Alizarin red S staining. The results revealed that the knockdown of ANX A1 in BM-MSCs exerts no apparent effect on the proliferation rate under normal conditions, however, following exposure to an osteogenic medium, downregulation of ANX A1 protected cells from the effect of osteogenic medium-induced inhibition of cell proliferation. Silencing ANX A1 with shRNA significantly inhibited the phosphorylation of extracellular signal-regulated kinase 1/2 and the expression of differentiation-associated genes (including runt-related transcription factor 2, osteopontin and osteocalcin) during osteogenesis and resulted in reduced differentiation of BM-MSCs. The results indicate the potential role of ANX A1 in the regulation of BM-MSC proliferation and osteogenic differentiation.

Estrogen modulates in vitro T cell responses in a concentration- and receptor-dependent manner: effects on intracellular molecular targets and antioxidant enzymes

Estrogen is a key hormone in facilitating ovulation and maintenance of pregnancy in young females and subsequent decline in its production contributes to the development of age-associated disorders such as hormone-dependent cancer, osteoporosis, and cardiovascular diseases. The mechanisms through which estrogen promotes female-specific diseases with advancing age are unclear especially, its effects on immune system which is vital for the maintenance of homeostasis and health. Although the diverse effects of estrogen on Th immunity (Th1 vs. Th2) have been characterized in several cell-types and animal models, there is no direct mechanistic study to understand its immunomodulatory actions. The purpose of this study is to investigate whether the in vitro effects of 17β-estradiol on lymphocytes from the spleen influence cell-mediated immune responses based on its concentration and type of estrogen receptors (ERs) and to assess its mechanism of action at the cellular level. Lymphocytes from the spleens of young Sprague-Dawley rats were isolated and incubated with various concentrations of 17β-estradiol (10(-6)-10(-14)M) and specific ERα- and β-agonists (10(-6)M, 10(-8)M and 10(-10)M) without or with concanavalin A (Con A) to measure T lymphocyte proliferation, IFN-γ and IL-2 production, p-ERK 1/2, p-CREB, and p-Akt, activities of antioxidant enzymes[superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)], and nitric oxide (NO) production. The specificity of ER-mediated actions in lymphocytes was examined by coincubation with nonspecific ER antagonists ICI(182,780) or tamoxifen. Lower concentrations of 17β-estradiol enhanced proliferation of T lymphocytes and IFN-γ production without or with Con A stimulation but had no effect on IL-2 production. ERα and ERβ agonists induced an increase in T cell proliferation and IFN-γ production and these effects were inhibited by tamoxifen. ERβ agonist alone enhanced IL-2 production by the lymphocytes. Coincubation with 17β-estradiol and ERα- and β-agonists augmented p-ERK 1/2, p-CREB, and p-Akt expression in the lymphocytes and tamoxifen reversed the ER agonist-induced effects on these molecular targets. Estrogen increased the activities of SOD, CAT, and GPx in both non-stimulated and Con A-stimulated splenocytes in a concentration-dependent manner. Both ERα- and β-agonists enhanced CAT and GPx activity while ERα-agonist decreased SOD activity and ERβ-agonist increased SOD activity. The effects of ER agonists on the antioxidant enzymes were reversed by ICI(182,780). Coincubation of lower doses of 17β-estradiol with Con A and both ER agonists enhanced NO production while higher dose of estrogen with Con A and ERα agonist suppressed its production and these effects were reversed by tamoxifen. Taken together, these results suggest that the effects of estrogen on the cell-mediated immune responses are dependent upon its concentrations and mediated through specific estrogen receptors involving intracellular signaling pathways and antioxidant enzymes.

Prednisolone exerts late mitogenic and biphasic effects on resistant acute lymphoblastic leukemia cells: Relation to early gene expression

Resistance or sensitivity to glucocorticoids is considered to be of crucial importance for disease prognosis in childhood acute lymphoblastic leukemia. Prednisolone exerted a delayed biphasic effect on the resistant CCRF-CEM leukemic cell line, necrotic at low doses and apoptotic at higher doses. At low doses, prednisolone exerted a pre-dominant mitogenic effect despite its induction on total cell death, while at higher doses, prednisolone's mitogenic and cell death effects were counterbalanced. Early gene microarray analysis revealed notable differences in 40 genes. The mitogenic/biphasic effects of prednisolone are of clinical importance in the case of resistant leukemic cells. This approach might lead to the identification of gene candidates for future molecular drug targets in combination therapy with glucocorticoids, along with early markers for glucocorticoid resistance.

Annexin-1 regulates growth arrest induced by high levels of estrogen in MCF-7 breast cancer cells

Estrogen, a naturally occurring female steroid growth hormone, has been implicated as a major risk factor for the development of breast cancer. Recent research into this disease has also correlated Annexin-1 (ANXA1), a glucocorticoid-inducible protein, with the development of breast tumorigenesis. ANXA1 is lost in many cancers, including breast cancer, and this may result in a functional promotion of tumor growth. In this study, we investigated the expression of ANXA1 in MCF-7 cells treated with estrogen and the regulation of estrogen functions by ANXA1. Exposure of MCF-7 breast cancer cells to high physiologic levels (up to 100 nmol/L) of estrogen leads to an up-regulation of ANXA1 expression partially through the activation of cyclic AMP-responsive element binding protein and dependency on activation of the estrogen receptor. In addition, treatment of MCF-7 cells with physiologic levels of estrogen (1 nmol/L) induced proliferation, whereas high pregnancy levels of estrogen (100 nmol/L) induced a growth arrest of MCF-7 cells, associated with constitutive activation of extracellular signal-regulated kinase 1/2 and up-regulation of cell cycle arrest proteins such as p21(waf/cip). Silencing of ANXA1 with specific small interfering RNA reverses the estrogen-dependent proliferation as well as growth arrest and concomitantly modulates extracellular signal-regulated kinase 1/2 phosphorylation. We confirm that ANXA1 is lost in clinical breast cancer, indicating that the antiproliferative protective function of ANXA1 against high levels of estrogen may be lost. Finally, we show that ANXA1-deficient mice exhibit faster carcinogen-induced tumor growth. Our data suggest that ANXA1 may act as a tumor suppressor gene and modulate the proliferative functions of estrogens.

Anti-Inflammatory Agents for Cancer Therapy

Inflammation is closely linked to cancer, and many anti-cancer agents are also used to treat inflammatory diseases, such as rheumatoid arthritis. Moreover, chronic inflammation increases the risk for various cancers, indicating that eliminating inflammation may represent a valid strategy for cancer prevention and therapy. This article explores the relationship between inflammation and cancer with an emphasis on epidemiological evidence, summarizes the current use of anti-inflammatory agents for cancer prevention and therapy, and describes the mechanisms underlying the anti-cancer effects of anti-inflammatory agents. Since monotherapy is generally insufficient for treating cancer, the combined use of anti-inflammatory agents and conventional cancer therapy is also a focal point in discussion. In addition, we also briefly describe future directions that should be explored for anti-cancer anti-inflammatory agents.

Dexamethasone-induced expression of endothelial mitogen-activated protein kinase phosphatase-1 involves activation of the transcription factors activator protein-1 and 3',5'-cyclic adenosine 5'-monophosphate response element-binding protein and the generation of reactive oxygen species

We have recently identified the MAPK phosphatase (MKP)-1 as a novel mediator of the antiinflammatory properties of glucocorticoids (dexamethasone) in the human endothelium. However, nothing is as yet known about the signaling pathways responsible for the up-regulation of MKP-1 by dexamethasone in endothelial cells. Knowledge of the molecular basis of this new alternative way of glucocorticoid action could facilitate the identification of new antiinflammatory drug targets. Thus, the aim of our study was to elucidate the underlying molecular mechanisms. Using Western blot analysis, we found that dexamethasone rapidly activates ERK, c-jun N-terminal kinase (JNK), and p38 MAPK in human umbilical vein endothelial cells. By applying the kinase inhibitors PD98059 (MAPK kinase-1) and SP600125 (JNK), ERK and JNK were shown to be crucial for the induction of MKP-1. Using EMSA and a decoy oligonucleotide approach, the transcription factors activator protein-1 (activated by ERK and JNK) and cAMP response element-binding protein (activated by ERK) were found to be involved in the up-regulation of MKP-1 by dexamethasone. Interestingly, dexamethasone induces the generation of reactive oxygen species (measured by dihydrofluorescein assay), which participate in the signaling process by triggering JNK activation. Our work elucidates a novel alternative mechanism for transducing antiinflammatory effects of glucocorticoids in the human endothelium. Thus, our study adds valuable information to the efforts made to find new antiinflammatory principles utilized by glucocorticoids. This might help to gain new therapeutic options to limit glucocorticoid side effects and to overcome resistance.

The influence of 17beta-estradiol on annexin 1 expression in the anterior pituitary of the female rat and in a folliculo-stellate cell line

Annexin 1 (ANXA1) is a Ca2+- and phospholipid-binding protein that plays an important role as a mediator of glucocorticoid action in the host-defence and neuroendocrine systems. Sex differences in hypothalamo-pituitary-adrenal (HPA) axis activity are well documented and a number of studies have demonstrated that gonadal steroids act as regulators of HPA activity. The aim of this study was to investigate the effect of ovariectomy and 17beta-estradiol replacement, and estrous cycle stage, on anterior pituitary ANXA1 content. The amount of anterior pituitary ANXA1 determined by western blotting varied with estrous cycle stage with a peak at estrus declining to a trough at proestrus. Ovariectomy resulted in a significant (P<0 x 05) decrease in anterior pituitary ANXA1 content. Administration of 17beta-estradiol (1 microg/100 g) significantly (P<0 x 01) increased anterior pituitary ANXA1 expression in the ovariectomized animals. In contrast, there was no change in pituitary ANXA1 content in response to 17beta-estradiol in adrenalectomized and adrenalectomized/ovariectomized rats. Treatment of TtT/GF cells, a folliculo-stellate cell line, with 17beta-estradiol (1 x 8-180 nM) increased ANXA1 mRNA expression and increased the amount of ANXA1 protein externalized in response to a dexamethasone stimulus. These results indicate that 17beta-estradiol stimulates ANXA1 expression in the anterior pituitary and in vivo an adrenal factor contributes to the mechanism of action.

Negative regulatory role of Annexin-A1 in 14-3-3η-mediated glucocorticoid receptor transcriptional activation

Annexin-A1 (ANX-1) is involved in glucocorticoid receptor (GR)-mediated signal transduction. However, the molecular mechanism by which ANX-1 plays a role in GR signaling is not fully understood. Recently, we reported that 14-3-3eta inhibits degradation of GR, resulting in an increase in GR transcriptional activity. In this study, we have addressed the role of ANX-1 in 14-3-3eta-induced enhancement of GR transactivation. ANX-1 abolished the increase in GR transcriptional activity due to 14-3-3eta. ANX-1 had no effect on the protein level of GR. However, ANX-1 abrogated the inhibitory effect of 14-3-3eta on GR degradation, which causes a decrease in GR stability in the nucleus. Our results indicate that ANX-1 functions as a negative regulator of GR transcriptional activation by inhibiting 14-3-3eta-induced up-regulation of GR.