Silencing of long non-coding RNA Sox2ot inhibits oxidative stress and inflammation of vascular smooth muscle cells in abdominal aortic aneurysm via microRNA-145-mediated Egr1 inhibition

Long non-coding RNAs (lncRNAs) have been largely reported to contribute to the development and progression of abdominal aortic aneurysm (AAA), a common vascular degenerative disease. The present study was set out with the aim to investigate the possible role of lncRNA Sox2ot in the development of AAA. In this study, we found that lncRNA Sox2ot and early growth response factor-1 (Egr1) were highly expressed, while microRNA (miR)-145 was poorly expressed in Ang II-induced AAA mice and oxidative stress-provoked vascular smooth muscle cell (VSMC) model. Egr1 was a potential target gene of miR-145, and lncRNA Sox2ot could competitively bind to miR-145 to upregulate Egr1 expression. Overexpression of miR-145-5p was found to attenuate oxidative stress and inflammation by inhibiting Egr1 both in vivo and in vitro, which was counteracted by lncRNA Sox2ot. Taken together, the present study provides evidence that downregulation of lncRNA Sox2ot suppressed the expression of Egr1 through regulating miR-145, thus inhibiting the development of AAA, highlighting a theoretical basis for AAA treatment.

Lysophosphatidic Acid Upregulates Recepteur D'origine Nantais Expression and Cell Invasion via Egr-1, AP-1, and NF-κB Signaling in Bladder Carcinoma Cells

Muscle invasive bladder carcinoma is a highly malignant cancer with a high mortality rate, due to its tendency to metastasize. The tyrosine kinase recepteur d’origine nantais (RON) promotes bladder carcinoma metastasis. Lysophosphatidic acid (LPA) is a phospholipid derivative, which acts as a signaling molecule to activate three high affinity G-protein coupled receptors, LPA1, LPA2, and LPA3. This in turn leads to cell proliferation and contributes to oncogenesis. However, little is known about the effects of LPA on invasive bladder cancer (IBC). In this study, we discovered that LPA upregulated RON expression, which in turn promoted cell invasion in bladder cancer T24 cells. As expected, we found that the LPA receptor was essential for the LPA induced increase in RON expression. More interestingly, we discovered that LPA induced RON expression via the MAPK (ERK1/2, JNK1/2), Egr-1, AP-1, and NF-κB signaling axes. These results provide experimental evidence and novel insights regarding bladder malignancy metastasis, which could be helpful for developing new therapeutic strategies for IBC treatment.

EGR1 promotes the cartilage degeneration and hypertrophy by activating the Krüppel-like factor 5 and β-catenin signaling

Osteoarthritis is one of the most common orthopedic diseases in elderly people who have lost their mobility. In this study，we observed abnormally high EGR1 expression in the articular cartilage of patients with osteoarthritis. We also found significantly high EGR1 expression in the articular cartilage of mice with destabilized medial meniscus (DMM)-induced osteoarthritis and 20-month-old mice. In vitro experiments indicated that IL-1β could significantly enhance EGR1 expression in primary mouse chondrocytes. EGR1 over-expression in chondrocytes using adenovirus could inhibit COl2A1 expression and enhance MMP9 and MMP13 expression. And silencing EGR1, using RNAi, had the opposite effects. Moreover, EGR1 over-expression accelerated chondrocyte hypertrophy in vitro, and EGR1 knockdown reversed this effect. We then explored the underlying mechanism. EGR1 over-expression increased Kruppel-Like Factor 5 (KLF5) protein level without influencing its synthesis. Enhanced EGR1 expression induced its integration with KLF5, leading to suppressed ubiquitination of KLF5. Moreover, EGR1 prompted β-catenin nuclear transportation to control chondrocyte hypertrophy. Ectopic expression of EGR1 in articular cartilage aggravated the degradation of the cartilage matrix in vivo. The EGR1 inhibitor, ML264, protected chondrocytes from IL-1β-mediated cartilage matrix degradation in vitro and DMM-induced osteoarthritis in vivo. Above all, we demonstrate the effect and mechanisms of EGR1 on osteoarthritis and provide evidence that the ML264 might be a potential drug for treating osteoarthritis in the future.

Downregulation of Egr-1 Expression Level via GluN2B Underlies the Antidepressant Effects of Ketamine in a Chronic Unpredictable Stress Animal Model of Depression

Ketamine is a non-competitive antagonist of N-methyl-D-aspartate receptors (NMDARs). Growing evidence suggests that a single dose of ketamine produces a series of rapid and remarkable antidepressant properties. However, the mechanisms remain unclear. In our study, the antidepressant properties of a single dose of ketamine (10 mg/kg, i.p.) in mice exposed to chronic unpredictable stress (CUS) were assessed using the open-field test (OFT) and the forced swimming test (FST). Early growth response 1 (Egr-1) and postsynaptic density protein 95 (PSD-95) mRNA and protein expression levels were examined using qRT-PCR and western blot, respectively. Dendritic spine density in the CA1 region of the hippocampus was detected by Golgi staining. AMPAR currents in hippocampal slices were measured by electrophysiology. Our study showed that CUS induced a significant depression-like behavior accompanied by an upregulation of Egr-1 and downregulations of PSD-95, spine density, and AMPAR currents in the hippocampus, and a single dose of ketamine rapidly restored these changes. Interestingly, a single dose of Ro-25-6981 (an GluN2B antagonist, 10 mg/kg, i.p.) or Egr-1 siRNA, but not NVP AAM077 (an GluN2A antagonist, 10 mg/kg, i.p.), could produce the same antidepressant effects as ketamine. These data demonstrate that ketamine may produce its rapid antidepressant effects by downregulating the expression of Egr-1 via blocking GluN2B in the hippocampus.

p53-dependent and -independent mechanisms are involved in (E)-1-(2-hydroxyphenyl)-3-(2-methoxynaphthalen-1-yl)prop-2-en-1-one (HMP)-induced apoptosis in HCT116 colon cancer cells

(E)-1-(2-hydroxyphenyl)-3-(2-methoxynaphthalen-1-yl)prop-2-en-1-one (HMP) is a novel synthetic naphthal chalcone derivative. The aim of this study was to investigate the mode of action underlying the antitumor activity of HMP. We found that treatment with HMP potently inhibited the clonogenicity and triggered cell death in HCT116 colon cancer cells. Flow cytometry showed that HMP induced an increase in the population of sub-G₀/G₁-phase cells. Annexin V binding assay revealed that HMP triggered apoptotic cell death. Furthermore, HMP stimulated the cleavages of caspase-7 and its substrate poly (ADP-ribose) polymerase (PARP). HMP promoted γ-H2AX formation and the production of reactive oxygen species (ROS), and up-regulated expression of the tumor suppressor p53. Interestingly, HMP-induced caspase-7 processing was not completely abrogated in p53-null (p53^-/-) HCT116 cells, suggesting that p53-dependent and -independent mechanisms are involved in HMP-induced apoptosis. Egr-1, a zinc finger transcription factor, was upregulated by HMP. Silencing of Egr-1 by shRNA significantly reduced HMP-induced caspase-7 and PARP cleavages, regardless of p53 status. These results suggest that HMP triggers caspase-mediated apoptosis through two distinct mechanisms involving p53-dependent and p53-independent, Egr-1-dependent pathways.

α-Bisabolol Inhibits Invasiveness and Motility in Pancreatic Cancer Through KISS1R Activation

α-Bisabolol is a plant-derived, oily sesquiterpene alcohol that induces apoptosis of various cancer cells. We previously reported the antiproliferative effects of α-bisabolol on pancreatic cancer cell lines using in vitro and in vivo experiments. However, the effects of α-bisabolol on tumor invasiveness and motility are still unknown. In this study, demonstrated that α-bisabolol suppressed the invasiveness and motility of a pancreatic cancer cell line. Although Early growth response 1 (EGR1) was involved in antiproliferative effects of α-bisabolol, it had no relationship with the inhibitory effect of α-bisabolol on cellular invasiveness and motility. Polymerase chain reaction analysis revealed that α-bisabolol induced Kisspeptin 1 receptor (KISS1R) in pancreatic cancer cell lines. The inhibition of KISS1R weakened the inhibitory effect of α-bisabolol on invasiveness of pancreatic cancer cells. The results also implied that the inhibitory effects of α-bisabolol on tumor invasiveness and motility are at least partly associated with the activation of KISS1R. However, there is a possibility that other molecular mechanisms of α-bisabolol regulate invasiveness and motility in pancreatic cancer cells. Further investigations are necessary to clarify the precise mechanisms of α-bisabolol activity for clinical application as a novel treatment for pancreatic cancer.

EGR1 regulates hepatic clock gene amplitude by activating Per1 transcription

The mammalian clock system is composed of a master clock and peripheral clocks. At the molecular level, the rhythm-generating mechanism is controlled by a molecular clock composed of positive and negative feedback loops. However, the underlying mechanisms for molecular clock regulation that affect circadian clock function remain unclear. Here, we show that Egr1 (early growth response 1), an early growth response gene, is expressed in mouse liver in a circadian manner. Consistently, Egr1 is transactivated by the CLOCK/BMAL1 heterodimer through a conserved E-box response element. In hepatocytes, EGR1 regulates the transcription of several core clock genes, including Bmal1, Per1, Per2, Rev-erbα and Rev-erbβ, and the rhythm amplitude of their expression is dependent on EGR1's transcriptional function. Further mechanistic studies indicated that EGR1 binds to the proximal region of the Per1 promoter to activate its transcription directly. When the peripheral clock is altered by light or feeding behavior transposition in Egr1-deficient mice, the expression phase of hepatic clock genes shifts normally, but the amplitude is also altered. Our data reveal a critical role for EGR1 in the regulation of hepatic clock circuitry, which may contribute to the rhythm stability of peripheral clock oscillators.

Inhibition of Egr1 expression underlies the anti-mitogenic effects of cAMP in vascular smooth muscle cells

AIMS

Cyclic AMP inhibits vascular smooth muscle cell (VSMC) proliferation which is important in the aetiology of numerous vascular diseases. The anti-mitogenic properties of cAMP in VSMC are dependent on activation of protein kinase A (PKA) and exchange protein activated by cAMP (EPAC), but the mechanisms are unclear.

METHODS AND RESULTS

Selective agonists of PKA and EPAC synergistically inhibited Egr1 expression, which was essential for VSMC proliferation. Forskolin, adenosine, A2B receptor agonist BAY60-6583 and Cicaprost also inhibited Egr1 expression in VSMC but not in endothelial cells. Inhibition of Egr1 by cAMP was independent of cAMP response element binding protein (CREB) activity but dependent on inhibition of serum response element (SRE) activity. SRF binding to the Egr1 promoter was not modulated by cAMP stimulation. However, Egr1 expression was dependent on the SRF co-factors Elk1 and 4 but independent of MAL. Inhibition of SRE-dependent Egr1 expression was due to synergistic inhibition of Rac1 activity by PKA and EPAC, resulting in rapid cytoskeleton remodelling and nuclear export of ERK1/2. This was associated with de-phosphorylation of the SRF co-factor Elk1.

CONCLUSION

cAMP inhibits VSMC proliferation by rapidly inhibiting Egr1 expression. This occurs, at least in part, via inhibition of Rac1 activity leading to rapid actin-cytoskeleton remodelling, nuclear export of ERK1/2, impaired Elk1-phosphorylation and inhibition of SRE activity. This identifies one of the earliest mechanisms underlying the anti-mitogenic effects of cAMP in VSMC but not in endothelial cells, making it an attractive target for selective inhibition of VSMC proliferation.

The role of egr1 in early zebrafish retinogenesis

Proper retinal cell differentiation is essential for establishing a functional retina. The purpose of this study is to investigate the role of early growth response 1 (egr1), a transcription factor (TF) that has been reported to control eye development and function, on retinal differentiation in zebrafish. Specifically, cellular changes in the Egr1-knockdown retinas were characterized by immunohistochemistry at 72 and 120 hours post-fertilization (hpf). The results indicate that Egr1 knockdown specifically suppressed the differentiation of subtypes of amacrine cells (ACs) and horizontal cells (HCs), including Parvalbumin- and GABA-positive ACs as well as Islet1-positive HCs. In addition, the knockdown induced a general delay of development of the other retinal cell types. These differentiation problems, particularly the ones with the ACs and HCs, also compromised the integrity of the inner and outer plexiform layers. In the Egr1-knockdown retinas, the expression of ptf1a, a TF that controls the specification of ACs and HCs, was prolonged and found in ectopic locations in the retina up to 72 hpf. Then, it became restricted to the proliferative marginal zone as in the control retinas at 120 hpf. This abnormal and prolonged expression of ptf1a during retinogenesis might affect the differentiation of ACs and HCs in the Egr1-knockdown retinas.

Egr-1 regulates the transcription of the BRCA1 gene by etoposide

The breast cancer susceptibility gene BRCA1 encodes a nuclear protein, which functions as a tumor suppressor and is involved in gene transcription and DNA repair processes. Many families with inherited breast and ovarian cancers have mutations in the BRCA1 gene. However, only a few studies have reported on the mechanism underlying the regulation of BRCA1 expression in humans. In this study, we investigated the transcriptional regulation of BRCA1 in HeLa cells treated with etoposide. We found that three Egr-1-binding sequences (EBSs) were located at -1031, -1005, and -385 within the enhancer region of the BRCA1 gene. Forced expression of Egr-1 stimulated the BRCA1 promoter activity. EMSA data showed that Egr-1 bound directly to the EBS within the BRCA1 gene. Knockdown of Egr-1 through the expression of a small hairpin RNA (shRNA) attenuated etoposide-induced BRCA1 promoter activity. We conclude that Egr-1 targets the BRCA1 gene in HeLa cells exposed to etoposide.

The protective effects of Egr-1 antisense oligodeoxyribonucleotide on cardiac microvascular endothelial injury induced by hypoxia-reoxygenation

Early growth response 1 (Egr-1) over-expression has been demonstrated in myocardial ischemia-reperfusion injury, which is closely associated with endothelial dysfunction. In the present study we investigated the expression of Egr-1 on cultured cardiac microvascular endothelial cells (CMECs) to help define the mechanism of myocardial ischemia-reperfusion injury. A model of cultured CMECs exposed to hypoxia-reoxygenation was developed in which synthesized Egr-1 sense and antisense oligodeoxyribonucleotide were transfected into the cells. The expression of Egr-1 was examined by Western blot analysis. Lactate dehydrogenase, malondialdehyde, superoxide dismutase, tumor necrosis factor alpha, and intercellular adhesion molecule 1 were measured after hypoxia-reoxygenation to assess cell function and injury. Cell morphology, cell viability, and neutrophil adhesion to the CMECs were measured to assess the degree of injury and inflammation. Only cells transfected with Egr-1 antisense oligodeoxyribonucleotide showed a significant reduction in Egr-1 protein expression following hypoxia-reoxygenation. Consistent with the down-regulation of Egr-1 expression, other forms of cell injury were significantly reduced in this group of cells, as evidenced by less alteration in cell morphology, a decrease in expression of tumor necrosis factor alpha and intercellular adhesion molecule 1, improved cell survival, and reduced neutrophil adhesion.

N-4-tert-butyl benzyl haloperidol chloride suppresses Ca2+-dependent Egr-1 expression and subsequently inhibits vascular smooth muscle cell proliferation induced by angiotensin II

BACKGROUND

N-4-Tert-Butyl benzyl haloperidol chloride (C(3)) was a novel calcium antagonist synthesized in our laboratory. The present study is to explore the effect of C(3) on vascular smooth muscle cell proliferation and the mechanism involved.

METHODS

The effects of C(3) on Ang II-induced cytosolic free Ca(2+) concentration change, VSMC proliferation, the key early growth response factor 1 (Egr-1) were evaluated by laser scanning confocal microscopy, microtiter tetrazolium (MTT) proliferation assay, flow cytometry analysis, Western blot and RT-PCR analysis, respectively. An extracellular Ca(2+) chelator EGTA and antisense Egr-1 oligodeoxyribonucleotides (ODNs) were used to establish the relation between Ca(2+)-dependent Egr-1 expression induced by Ang II and VSMC proliferation.

RESULTS

C(3) attenuated the Ang II-induced extracellular Ca(2+) influx, inhibited VSMCs proliferation and arrested VSMCs in G(1)-phase. C(3) also triggered a significant reduction in PDGF-A and cyclin D1, Cdk2 along with an overexpression of p21Cip1. Antisense Egr-1 ODNs inhibited VSMCs proliferation, which was related to G(1)-phase arrest, due to inhibiting the expression of Egr-1 and C(3) inhibited the overexpression of Egr-1.

CONCLUSION

Egr-1 may play a key role in Ang II-induced proliferation of VSMCs. C(3) inhibits vascular smooth muscle cell proliferation and the mechanism is involved with the inhibition of over-expression of Egr-1.

Antithrombin inhibits lipopolysaccharide-induced tumor necrosis factor-alpha production by monocytes in vitro through inhibition of Egr-1 expression

BACKGROUND

Antithrombin (AT) improves the outcome of septic patients with intravascular coagulation. However, the mechanisms underlying the therapeutic benefits of AT are not fully understood. Tumor necrosis factor-alpha (TNF-alpha) plays a critical role in the development of organ failure and intravascular coagulation in sepsis.

AIM

This study aimed to elucidate a molecular mechanism by which AT inhibits TNF-alpha production.

METHODS

Human peripheral monocyte was stimulated by lipopolysaccharide (LPS) and TNF-alpha concentration in media was measured. Levels of phosphorylation of extracellular signal-regulated protein kinases (ERK) 1/2 and early growth response factor-1 (Egr-1) were estimated by western blotting or by electrophoretic mobility shift assay.

RESULTS

Antithrombin (3 U mL(-1)) inhibited TNF-alpha production by monocytes stimulated with LPS. Conversely, chemically modified AT that lacks affinity for heparin did not. AT inhibited the phosphorylation of ERK 1/2 and decreased the expression of Egr-1 in LPS-stimulated monocytes. However, it did not affect the activation of either nuclear factor-kappaB or activator protein-1. Pretreatment with KT5720, a protein kinase A inhibitor, reversed the inhibitory effect of AT on the LPS-induced phosphorylation of ERK1/2. Although 2 U mL(-1) AT slightly inhibited TNF-alpha production by LPS-stimulated monocytes, it significantly inhibited TNF-alpha production in the presence of a low concentration of beraprost, a stable derivative of prostacyclin.

CONCLUSIONS

These observations suggest that AT might inhibit LPS-induced production of TNF-alpha by inhibiting the increase in Egr-1 expression in monocytes via interaction with heparin-like substances expressed on the cell surface.

Transfected synthetic DNA enzyme gene specifically inhibits Egr-1 gene expression and reduces neointimal hyperplasia following balloon injury in rats

BACKGROUND

Early growth response factor-1 (Egr-1) controls the gene expression involved in postangioplasty restenosis. In the present study we synthesized specific catalytic DNA targeting sequences in human Egr-1 mRNA to investigate the effects on artery balloon injury.

METHODS

The catalytic DNA, ED5, was synthesized and transfected into the arterial wall of Wistar rats using the FuGENE6 transfection reagent. The animals were euthanized at day 3, 7, 14 and 21 following artery balloon injury. Serum nitric oxide (NO), nitric oxide synthase (NOS), and endothelin (ET) levels were measured before sacrifice. Histopathological changes to the arterial tissue were evaluated by H&E staining and observed via transmission electromicroscopy. Egr-1, PCNA and TGF-beta(1) expression was detected by immunohistochemistry, RT-PCR, and western-blot.

RESULTS

Compared with the control groups, ED5-treated rats exhibited increased levels of both NO and NOS (p<0.05); by contrast, plasma ET levels were decreased relative to controls (p<0.05). Neointimal hyperplasia (NH) was significantly reduced and vascular smooth muscle cells (VSMCs) in the neointima exhibited a general contractile phenotype. Both protein and mRNA expression of Egr-1, PCNA, and TGF-beta(1) in the ED5-treated group were decreased at each time point (p<0.001).

CONCLUSIONS

ED5 may specifically inhibit Egr-1 gene expression and reduce NH after balloon injury in rats; the latter effect may be mediated by a down-regulation of TGF-beta(1) and up-regulation of NOS to inhibit NH following balloon injury.

Effects of antisense oligonucleotides to mRNA for the early gene zif268 on the mechanisms of synapse-specific plasticity

Acquisition of nociceptive sensitization in common snails was accompanied by long-term facilitation of the responses of defensive behavior command neuron LPl1 to sensory stimulation of chemoreceptors on the head and mechanoreceptors on the head and foot. Acquisition of sensitization during intracellular administration of antisense oligonucleotides to mRNA encoding the early gene zif268 showed suppression of synaptic facilitation in the responses of neuron LPl1 to tactile and chemical stimulation of the snail's head. Synaptic facilitation in the responses to tactile stimulation of the foot developed as in neurons of control sensitized animals. These results suggest that the early gene zif268 is selectively involved in the mechanisms of the specific regulation of the synaptic inputs of neuron LPl1 from sensory receptors on the snail's head.

Expression of the heparan sulfate-degrading enzyme heparanase is induced in infiltrating CD4+ T cells in experimental autoimmune encephalomyelitis and regulated at the level of transcription by early growth response gene 1

The heparan sulfate-cleaving enzyme heparanase (HPSE) plays an important role in remodeling of the basement membrane and extracellular matrix during inflammation. Inducible HPSE enzymatic activity has been reported in leukocytes; however, little is known of the molecular mechanisms that regulate HPSE gene expression during inflammatory disease. In this study, HPSE expression and regulation in the T cell-mediated disease model, experimental autoimmune encephalomyelitis (EAE), were investigated. Expression analysis showed that HPSE mRNA is induced in rat CD4+ antigen-specific T lymphocytes upon activation and correlates with the encephalitogenicity of the cells. Examination of the kinetics and cell type-specific expression of HPSE throughout the progression of active EAE in rats, indicated that HPSE was highly expressed in CD4+ T cells infiltrating the central nervous system (CNS) during clinical disease. Little or no HPSE expression was observed in CD8+ T cells, macrophages, or astrocytes during disease progression. To investigate the mechanism of inducible HPSE gene regulation in T cells, studies were extended into human primary T cells. HPSE mRNA, protein, and enzymatic activity were induced upon activation. Functional analysis of the human HPSE promoter identified an EGR1 binding motif that contained high inducible activity and was transactivated by EGR1. Furthermore, the treatment of primary T lymphocytes with an EGR1 siRNA inhibited inducible HPSE mRNA expression. These data provide evidence to suggest that inducible HPSE expression in primary T lymphocytes is regulated at the transcriptional level by EGR1 and is important in facilitating CD4+ T cell infiltration into the CNS to promote EAE.

Interleukin-1 beta-induced Id2 gene expression is mediated by Egr-1 in vascular smooth muscle cells

OBJECTIVE

Id2 (inhibitor of DNA-binding 2), a member of the helix-loop-helix family of transcription regulators, plays important roles in cell proliferation and differentiation. Recent reports have documented that Id2 is up-regulated during vascular lesion formation and overexpression of Id2 promotes vascular smooth muscle cell (VSMC) proliferation. However, the transcriptional regulation of Id2 gene expression in VSMC remains unexplored.

METHODS AND RESULTS

Using Northern- and Western-blot analyses, we documented that interleukin-1beta (IL-1beta) induced Id2 gene expression in VSMC in a time- and dose-dependent manner. Overexpression of early growth response-1 (Egr-1) in VSMC induced Id2 expression while IL-1beta-induced Id2 expression was abrogated in VSMC by the Egr-1 repressor, NGFI-A binding protein 2 (NAB2), expressed from an adenovirus. Overexpression of Egr-1 transactivated the Id2 promoter in reporter assays dependent on the presence of intact putative Egr-1 binding sites as determined by mutagenesis. Finally, electrophoretic mobility shift assays (EMSA) demonstrated that the Egr-1 protein can bind the Egr-1 sites derived from the human Id2 promoter in vitro and chromatin immunoprecipitation identified the putative Egr-1 site between -723 to -712 as the functional Egr-1 binding site in vivo.

CONCLUSIONS

Our data demonstrate that IL-1beta-induced Id2 expression in VSMC is mediated by the transcription factor Egr-1 in VSMC.

Carvedilol, a nonselective beta-blocker, suppresses the production of tumor necrosis factor and tissue factor by inhibiting early growth response factor-1 expression in human monocytes in vitro

Tumor necrosis factor (TNF) and tissue factor (TF) produced by monocytes and macrophages have been shown to be among the aggravating factors for chronic heart failure (CHF), because they induce cardiac dysfunction and thrombotic complications, respectively. Carvedilol, a nonselective beta-adrenoceptor antagonist with alpha(1)- adrenoceptor blockade action, has been demonstrated to improve the outcome of patients with severe CHF, suggesting that carvedilol might inhibit the production of TNF and TF. In this study, this possibility is examined using isolated human monocytes stimulated with lipopolysaccharide (LPS) in vitro. Carvedilol (10 muM) significantly inhibited LPS-induced production of TNF and TF by monocytes, whereas prazosin (a selective alpha(1)-adrenoceptor antagonist), bisoprolol (a selective beta(1)-adrenoceptor antagonist), ICI-118,551 (a selective beta(2)-adrenoceptor antagonist), and arotinolol (a nonselective beta-adrenoceptor antagonist with alpha(1)-adrenoceptor blockade action) did not. Carvedilol inhibited both expression of early growth response factor-1 (Egr-1) and phosphorylation of extracellular signal-regulated kinase (ERK) 1/2, but it did not inhibit activation of either nuclear factor-kappaB or activator protein-1 in monocytes stimulated with LPS. These results suggest that carvedilol inhibits LPS-induced production of TNF and TF by inhibiting activation of the ERK1/2-Egr-1 pathway independent of its adrenoceptor inhibitory activities in monocytes.

Maximal activity of the luteinizing hormone beta-subunit gene requires beta-catenin

GnRH regulates expression of LHB via transcriptional regulation of early growth response 1 (EGR1), an immediate early gene that encodes a zinc-finger DNA-binding protein. EGR1 interacts functionally with the orphan nuclear receptor steroidogenic factor 1 (SF1) and pituitary homeobox 1, a member of the paired-like homeodomain family. The functional synergism of this tripartite interaction defines the maximal level of LHB transcription that can occur in response to GnRH. Results presented herein provide new evidence that the interaction between SF1 and EGR1 also requires beta-catenin, a transcriptional coactivator and member of the canonical Wnt signaling pathway. For instance, targeted reduction of beta-catenin attenuates activity of a GnRH-primed LHB promoter. Additional gene reporter assays indicate that overexpression of beta-catenin, or its targeted reduction by small interfering RNA, modulates activity of both SF1 and EGR1 as well as their functional interaction. beta-Catenin coimmunoprecipitates with SF1. Moreover, an SF1 mutant that lacks a beta-catenin binding domain has compromised transcriptional activity and fails to interact synergistically with EGR1. Finally, GnRH promotes beta-catenin colocalization with SF1 and EGR1 on the endogenous mouse Lhb promoter-regulatory region. Taken together, these data suggest that beta-catenin binds to SF1 and that this interaction is required for subsequent functional interaction with EGR1. Thus, these data identify beta-catenin as a new and required member of the basal transcriptional complex that allows the LHB promoter to achieve maximal activity in response to GnRH.

Local and descending circuits regulate long-term potentiation and zif268 expression in spinal neurons

Long-term potentiation (LTP), a use dependent long-lasting modification of synaptic strength, was first discovered in the hippocampus and later shown to occur in sensory areas of the spinal cord. Here we demonstrate that spinal LTP requires the activation of a subset of superficial spinal dorsal horn neurons expressing the neurokinin-1 receptor (NK1-R) that have previously been shown to mediate certain forms of hyperalgesia. These neurons participate in local spinal sensory processing, but are also the origin of a spino-bulbo-spinal loop driving a 5-hydroxytryptamine 3 receptor (5HT3-R)- mediated descending facilitation of spinal pain processing. Using a saporin-substance P conjugate to produce site-specific neuronal ablation, we demonstrate that NK1-R expressing cells in the superficial dorsal horn are crucial for the generation of LTP-like changes in neuronal excitability in deep dorsal horn neurons and this is modulated by descending 5HT3-R-mediated facilitatory controls. Hippocampal LTP is associated with early expression of the immediate-early gene zif268 and knockout of the gene leads to deficits in long-term LTP and learning and memory. We found that spinal LTP is also correlated with increased neuronal expression of zif268 in the superficial dorsal horn and that zif268 antisense treatment resulted in deficits in the long-term maintenance of inflammatory hyperalgesia. Our results support the suggestion that the generation of LTP in dorsal horn neurons following peripheral injury may be one mechanism whereby acute pain can be transformed into a long-term pain state.

The role of MAPKs in B cell receptor-induced down-regulation of Egr-1 in immature B lymphoma cells

Cross-linking of the B cell receptor (BCR) on the immature B lymphoma cell line BKS-2 induces growth inhibition and apoptosis accompanied by rapid down-regulation of the immediate-early gene egr-1. In these lymphoma cells, egr-1 is expressed constitutively and has a prosurvival role, as Egr-1-specific antisense oligonucleotides or expression of a dominant-negative inhibitor of Egr-1 also prevented the growth of BKS-2 cells. Moreover, enhancement of Egr-1 protein with phorbol 12-myristate 13-acetate or an egr-1 expression vector rescued BKS-2 cells from BCR signal-induced growth inhibition. Nuclear run-on and mRNA stability assays indicated that BCR-derived signals act at the transcriptional level to reduce egr-1 expression. Inhibitors of ERK and JNK (but not of p38 MAPK) reduced egr-1 expression at the protein level. Transcriptional regulation appears to have a role because egr-1 promoter-driven luciferase expression was reduced by ERK and JNK inhibitors. Promoter truncation experiments suggested that several serum response elements are required for MAPK-mediated egr-1 expression. Our study suggests that BCR signals reduce egr-1 expression by inhibiting activation of ERK and JNK. Unlike ERK and JNK, p38 MAPK reduces constitutive expression of egr-1. Unlike the immature B lymphoma cells, normal immature B cells did not exhibit constitutive MAPK activation. BCR-induced MAPK activation was modest and transient with a small increase in egr-1 expression in normal immature B cells consistent with their inability to proliferate in response to BCR cross-linking.

Cigarette smoke-induced Egr-1 upregulates proinflammatory cytokines in pulmonary epithelial cells

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death worldwide and is a progressive and irreversible disorder. Cigarette smoking is associated with 80-90% of COPD cases; however, the genes involved in COPD-associated emphysema and chronic inflammation are poorly understood. It was recently demonstrated that early growth response gene 1 (Egr-1) is significantly upregulated in the lungs of smokers with COPD (Ning W and coworkers, Proc Natl Acad Sci 2004;101:14895-14900). We hypothesized that Egr-1 is activated in pulmonary epithelial cells during exposure to cigarette smoke extract (CSE). Using immunohistochemistry, we demonstrated that pulmonary adenocarcinoma cells (A-549) and primary epithelial cells lacking basal Egr-1 markedly induce Egr-1 expression after CSE exposure. To evaluate Egr-1-specific effects, we used antisense (alphaS) oligodeoxynucleotides (ODN) to knock down Egr-1 expression. Incorporation of Egr-1 alphaS ODN significantly decreased CSE-induced Egr-1 mRNA and protein, while sense ODN had no effect. Via Egr-1-mediated mechanisms, IL-1beta and TNF-alpha were significantly upregulated in pulmonary epithelial cells exposed to CSE or transfected with Egr-1. To investigate the relationship between Egr-1 induction by smoking and susceptibility to emphysema, we determined Egr-1 expression in strains of mice with different susceptibilities for the development of smoking-induced emphysema. Egr-1 was markedly increased in the lungs of emphysema-susceptible AKR/J mice chronically exposed to cigarette smoke, but only minimally increased in resistant NZWLac/J mice. In conclusion, Egr-1 is induced by cigarette smoke and functions in proinflammatory mechanisms that likely contribute to the development of COPD in the lungs of smokers.

Curcumin inhibits human colon cancer cell growth by suppressing gene expression of epidermal growth factor receptor through reducing the activity of the transcription factor Egr-1

High expression of epidermal growth factor receptor (EGFR) is found in a variety of solid tumors, including colorectal cancer. EGFR has been identified as a rational target for anticancer therapy. Curcumin, the yellow pigment of turmeric in curry, has received attention as a promising dietary supplement for cancer prevention and treatment. We recently reported that curcumin inhibited the growth of human colon cancer-derived Moser cells by suppressing gene expression of cyclinD1 and EGFR. The aim of the present study was to explore the molecular mechanisms underlying curcumin inhibition of gene expression of EGFR in colon cancer cells. The generality of the inhibitory effect of curcumin on gene expression of EGFR was verified in other human colon cancer-derived cell lines, including Caco-2 and HT-29 cells. Promoter deletion assays and site-directed mutageneses identified a binding site for the transcription factor early growth response-1 (Egr-1) in egfr promoter as a putative curcumin response element in regulating the promoter activity of the gene in Moser cells. Electrophoretic mobility shift assays demonstrated that curcumin significantly reduced the DNA-binding activity of the transcription factor Egr-1 to the curcumin response element. In addition, curcumin reduced the trans-activation activity of Egr-1 by suppressing egr-1 gene expression, which required interruption of the ERK signal pathway and reduction of the level of phosphorylation of Elk-1 and its activity. Taken together, our results demonstrated that curcumin inhibited human colon cancer cell growth by suppressing gene expression of EGFR through reducing the trans-activation activity of Egr-1. These results provided novel insights into the mechanisms of curcumin inhibition of colon cancer cell growth and potential therapeutic strategies for treatment of colon cancer.

Suppression of Egr-1 transcription through targeting of the serum response factor by oncogenic H-Ras

The transcription factor Egr-1 functions as a key regulator in cellular growth, differentiation, and apoptosis. The loss of Egr-1 expression is closely associated with tumor development, although the molecular mechanism behind the suppression of Egr-1 is largely unknown. In this report, we show that growth factor-induced transcriptional activation of Egr-1 gene is downregulated by chronic expression of oncogenic H-Ras in NIH3T3 fibroblasts. Our results demonstrate that phosphoinositide 3-kinase (PI3K) signaling is necessary for oncogenic H-Ras-mediated reduction of Egr-1 gene expression. Aberrant activation of PI3K signaling by oncogenic Ras decreased the level of serum response factor (SRF) protein through the acceleration of proteolysis, which resulted in decreased SRF binding to the serum response element (SRE) sites within the Egr-1 promoter, leading to the suppression of Egr-1 transcription. Inhibition of PI3K signaling restored the downregulation of SRF and Egr-1 expression caused by oncogenic Ras. Our findings suggest a novel signaling mechanism by which prolonged activation of oncogenic H-Ras can trigger the loss of tumor suppressor Egr-1 through the PI3K pathway in NIH3T3 fibroblast model cell lines.

Disrupting reconsolidation of drug memories reduces cocaine-seeking behavior

Maladaptive memories that associate environmental stimuli with the effects of drugs of abuse are known to be a major cause of relapse to, and persistence of, a drug addictive habit. However, memories may be disrupted after their acquisition and consolidation by impairing their reconsolidation. Here, we show that infusion of Zif268 antisense oligodeoxynucleotides into the basolateral amygdala, prior to the reactivation of a well-learned memory for a conditioned stimulus (CS)-cocaine association, abolishes the acquired conditioned reinforcing properties of the drug-associated stimulus and thus its impact on the learning of a new cocaine-seeking response. Furthermore, we show that reconsolidation of CS-fear memories also requires Zif268 in the amygdala. These results demonstrate that appetitive CS-drug memories undergo reconsolidation in a manner similar to aversive memories and that this amygdala-dependent reconsolidation can be disrupted to reduce the impact of drug cues on drug seeking.