Extinguishing Egr-1-dependent inflammatory and thrombotic cascades after lung transplantation

Liproxstatin-1 Alleviated Ischemia/Reperfusion-Induced Acute Kidney Injury via Inhibiting Ferroptosis

Ferroptosis, as a novel regulable cell death, is characterized by iron overload, glutathione depletion, and an accumulation of lipid peroxides. Recently, it has been discovered that ferroptosis is involved in ischemia/reperfusion (I/R)-induced acute kidney injury (AKI) and plays a crucial role in renal tubular cell death. In this study, we tried to investigate the effect and mechanism of liproxstatin-1 (Lip-1) in I/R-induced AKI and seek the key regulator of ferroptosis in I/R-induced AKI. Mice were administrated with clamping bilateral renal pedicles for 30 min. We found that early growth response 1 (EGR1) might be a key regulator of ferroptosis, and Lip-1 could suppress ferroptosis via EGR1. Meanwhile, Lip-1 could reduce macrophage recruitment and the release of inflammatory cytokines. These findings indicated that Lip-1 alleviated I/R-induced AKI via regulating EGR1, and it might pave the theoretical basis of a new therapeutic strategy for I/R-induced AKI.

Early Growth Response-1: Friend or Foe in the Heart?

Cardiovascular disease is a major cause of mortality and morbidity worldwide. Early growth response-1 (Egr-1) plays a critical regulatory role in a range of experimental models of cardiovascular diseases. Egr-1 is an immediate-early gene and is upregulated by various stimuli including shear stress, oxygen deprivation, oxidative stress and nutrient deprivation. However, recent research suggests a new, underexplored cardioprotective side of Egr-1. The main purpose of this review is to explore and summarise the dual nature of Egr-1 in cardiovascular pathobiology.

The Egr-1/miR-15a-5p/GPX4 axis regulates ferroptosis in acute myocardial infarction

Acute myocardial infarction (AMI) is a type of cardiovascular diseases that severely threatens human being, but the mechanisms have not been thoroughly clarified. Here, we detected that microRNA-15a-5p (miR-15a-5p) was up-regulated in AMI. Knockdown of miR-15a-5p reduced cell mortality in hypoxic-treated myocardial cells. In addition, we determined that glutathione peroxidase4 (GPX4) was the direct target of miR-15a-5p by luciferase reporter assay. Over-expression of miR-15a-5p strengthened ferroptosis, then aggravated myocardial cell hypoxia injury. Mechanistically, silencing transcription factor early growth response-1 (Egr-1) inhibited the level of miR-15a-5p, increased the protein expression of GPX4, accompanied by reduced ferroptosis and alleviated myocardial injury. In summary, these results provide a novel signaling pathway during the progression of acute myocardial infarction, namely Egr-1/miR-15a-5p/GPX4/ferroptosis.

Transcription factor EGR-1 transactivates the MMP1 gene promoter in response to TNFα in HaCaT keratinocytes

Matrix metalloproteinase 1 (MMP-1), a calcium-dependent zinc- containing collagenase, is involved in the initial degradation of native fibrillar collagen. Tissue necrosis factor-alpha (TNFα) is a pro-inflammatory cytokine that is rapidly produced by dermal fibroblasts, monocytes/macrophages, and keratinocytes and regulates inflammation and damaged-tissue remodeling. MMP-1 is induced by TNFα and plays a critical role in tissue remodeling and skin aging processes. However, the regulation of the MMP1 gene by TNFα is not fully understood. We aimed to find additional cis-acting elements involved in the regulation of TNFα-induced MMP1 gene transcription in addition to the nuclear factor-kappa B (NF-kB) and activator protein 1 (AP1) sites. Assessments of the 5’-regulatory region of the MMP1 gene, using a series of deletion constructs, revealed the requirement of the early growth response protein 1 (EGR-1)-binding sequence (EBS) in the proximal region for proper transcription by TNFα. Ectopic expression of EGR-1, a zinc-finger transcription factor that binds to G-C rich sequences, stimulated MMP1 promoter activity. The silencing of EGR-1 by RNA interference reduced TNFα-induced MMP-1 expression. EGR-1 directly binds to the proximal region and transactivates the MMP1 gene promoter. Mutation of the EBS within the MMP1 promoter abolished EGR-1-mediated MMP-1 promoter activation. These data suggest that EGR-1 is required for TNFα-induced MMP1 transcriptional activation. In addition, we found that all three MAPKs, ERK1/2, JNK, and p38 kinase, mediate TNFα-induced MMP-1 expression via EGR-1 upregulation. These results suggest that EGR-1 may represent a good target for the development of pharmaceutical agents to reduce inflammation-induced MMP-1 expression.

Mechanistic regulation of SPHK1 expression and translocation by EMAP II in pulmonary smooth muscle cells

Phosphorylation of sphingosine by sphingosine kinase 1 (SPHK1) produces the bioactive sphingolipid sphingosine-1-phosphate (S1P), a microvascular and immuno-modulator associated with vascular remodeling in pulmonary arterial hypertension (PAH). The low intracellular concentration of S1P is under tight spatial-temporal control. Molecular mechanisms that mediate S1P burden and S1P regulation of vascular remodeling are poorly understood. Similarities between two early response pro-inflammatory cytokine gene transcript activation profiles, S1P and Endothelial Monocyte Activating Polypeptide II (EMAP II), suggested a strategic link between their signaling pathways. We determined that EMAP II triggers a bimodal phosphorylation, transcriptional regulation and membrane translocation of SPHK1 through a common upstream process in both macrophages and pulmonary artery smooth muscle cells (PASMCs). EMAP II initiates a dual function of ERK1/2: phosphorylation of SPHK1 and regulation of the transcription factor EGR1 that induces expression of SPHK1. Activated ERK1/2 induces a bimodal phosphorylation of SPHK1 which reciprocally increases S1P levels. This identified common upstream signaling mechanism between a protein and a bioactive lipid initiates cell specific downstream signaling representing a multifactorial mechanism that contributes to inflammation and PASMC proliferation which are cardinal histopathological phenotypes of PAH.

A Functional Polymorphism-Mediated Disruption of EGR1/ADAM10 Pathway Confers the Risk of Sepsis Progression

Increasing evidence has indicated that single nucleotide polymorphisms (SNPs) are related to the susceptibility of sepsis and might provide potential evidence for the mechanisms of sepsis. Our recent preliminary study showed that the ADAM10 genetic polymorphism was clinically associated with the development of sepsis, and little is known about the underlying mechanism. The aim of this study was to confirm the association between the ADAM10 promoter rs653765 G→A polymorphism and the progression of sepsis and to discover the underlying mechanism. Clinical data showed that the rs653765 G→A polymorphism was positively correlated with the development of sepsis, as evidenced by a multiple-center case-control association study with a large sample size, and showed that EGR1 and ADAM10 levels were associated well with the different subtypes of sepsis patients. In vitro results demonstrated that the rs653765 G→A variants could functionally modulate ADAM10 promoter activity by altering the binding of the EGR1 transcription factor (TF) to the ADAM10 promoter, affecting the transcription and translation of the ADAM10 gene. Electrophoretic mobility shift assay (EMSA) followed by chromatin immunoprecipitation (ChIP) assay indicated the direct interaction. Functional studies further identified that the EGR1/ADAM10 pathway is important for the inflammatory response. EGR1 intervention in vivo decreased host proinflammatory cytokine secretion and rescued the survival and tissue injury of the mouse endotoxemia model.IMPORTANCE Sepsis is characterized as life-threatening organ dysfunction, with unacceptably high mortality. Evidence has indicated that functional SNPs within inflammatory genes are associated with susceptibility, progression, and prognosis of sepsis. These mechanisms on which these susceptible sites depended often suggest the key pathogenesis and potential targets in sepsis. In the present study, we confirmed that a functional variant acts as an important genetic factor that confers the progression of sepsis in a large sample size and in multiple centers and revealed that the variants modulate the EGR1/ADAM10 pathway and influence the severity of sepsis. We believe that we provide an important insight into this new pathway involving the regulation of inflammatory process of sepsis based on the clinical genetic evidence, which will enhance the understanding of nosogenesis of sepsis and provide the potential target for inflammation-related diseases.

Gene expression analysis of follicular cells revealed inflammation as a potential IVF failure cause

PURPOSE

Hormonal stimulation prior to IVF influences the ovarian environment and therefore impacts oocytes and subsequent embryo quality. Not every patient has the same response to the same treatment and many fail for unknown reasons. Knowing why a cycle has failed and how the follicles were affected would allow clinicians to adapt the treatment accordingly and improve success rate. This study examines the hypothesis that transcriptomic analysis of follicular cells from failed IVF cycles reveals potential reasons for failure and provides new information on the physiological mechanisms related to IVF failure.

METHODS

Follicular cells (granulosa cells) were obtained from IVF patients of four Canadian fertility clinics. Using microarray analysis, patients that did not become pregnant following the IVF cycle were compared to those that did. Functional analysis was performed using ingenuity pathway analysis and qRT-PCR was used to validate the microarray results in a larger cohort of patients.

RESULTS

The microarray showed 165 differentially expressed genes (DEGs) in the negative group compared to the pregnancy group. DEGs include many pro-inflammatory cytokines and other factors related to inflammation, suggesting that this process might be altered when IVF fails. Overexpression of several factors, some of which act upstream from vascular endothelial growth factor (VEGF), also indicates increased permeability and vasodilation. Some DEGs were related to abnormal differentiation and increased apoptosis.

CONCLUSIONS

Our results suggest that failure to conceive following IVF cycles could be associated with an imbalance between pro-inflammatory and anti-inflammatory mediators. The findings of this study identify potential failure causes and pathways for further investigation. Stimulatory protocols personalized according to patient response could improve the chances of later success.

Early Growth Response-1 Plays an Important Role in Ischemia-Reperfusion Injury in Lung Transplants by Regulating Polymorphonuclear Neutrophil Infiltration

BACKGROUND

Early growth response-1 (Egr-1) has been shown to be a trigger-switch transcription factor that is involved in lung ischemia-reperfusion injury (IRI).

METHODS

Mouse lung transplants were performed in wild-type (WT) C57BL/6 and Egr1-knockout (KO) mice in the following donor → recipient combinations: WT → WT, KO → WT, WT → KO, and KO → KO to determine whether the presence of Egr-1 in the donor or recipient is the most critical factor for IRI. Pulmonary grafts were retrieved after 18 hours of ischemia after 4 hours of reperfusion. We analyzed graft function by analyzing arterial blood gas and histology in each combination and assessed the effects of Egr1 depletion on inflammatory cytokines that are regulated by Egr-1 as well on polymorphonuclear neutrophil (PMN) infiltration.

RESULTS

Deletion of Egr1 improved pulmonary graft function in the following order of donor → recipient combinations: WT → WT < WT → KO < KO → WT < KO → KO. Polymerase chain reaction assays for Il1B, Il6, Mcp1, Mip2, Icam1, and Cox2 showed significantly lower expression levels in the KO → KO group than in the other groups. Immunohistochemistry demonstrated clear Egr-1 expression in the nuclei of pulmonary artery endothelial cells and PMN cytoplasm in the WT grafts. Flow cytometry analysis showed that Egr1 deletion reduced PMN infiltration and that the extent of reduction correlated with graft function.

CONCLUSIONS

Both graft and recipient Egr-1 played a role in lung IRI, but the graft side contributed more to this phenomenon through regulation of PMN infiltration. Donor Egr-1 expression in pulmonary artery endothelial cells may play an important role in PMN infiltration, which results in IRI after lung transplantation.

Pioglitazone Identifies a New Target for Aneurysm Treatment: Role of Egr1 in an Experimental Murine Model of Aortic Aneurysm

Peroxisome proliferator-activated receptor x03B3; agonists have been shown to inhibit angiotensin II (AngII)-induced experimental abdominal aortic aneurysms. Macrophage infiltration to the vascular wall is an early event in this pathology, and therefore we explored the effects of the peroxisome proliferator-activated receptor x03B3; agonist pioglitazone on AngII-treated macrophages. Using microarray-based expression profiling of phorbol ester-stimulated THP-1 cells, we found that a number of aneurysm-related gene changes effected by AngII were modulated following the addition of pioglitazone. Among those genes, polycystic kidney disease 1 (PKD1) was significantly up-regulated (multiple testing corrected p < 0.05). The analysis of the PKD1 proximal promoter revealed a putative early growth response 1 (EGR1) binding site, which was confirmed by chromatin immunoprecipitation (ChIP) and quantitative PCR. Further analysis of publicly available ChIP-sequencing data revealed that this putative binding site overlapped with a conserved EGR1 binding peak present in 5 other cell lines. Quantitative real-time PCR showed that EGR1 suppressed PKD1, while AngII significantly up-regulated PKD1, an effect counteracted by pioglitazone. Conversely, in EGR1 short hairpin RNA lentivirally transduced THP-1 cells, reduced EGR1 led to a significant up-regulation of PKD1, especially after treatment with pioglitazone. In vivo, deficiency of Egr1 in the haematopoietic compartment of mice completely abolished the incidence of CaCl2-induced aneurysm formation.

Novel regulatory action of ribosomal inactivation on epithelial Nod2-linked proinflammatory signals in two convergent ATF3-associated pathways

In response to excessive nucleotide-binding oligomerization domain-containing protein 2 (Nod2) stimulation caused by mucosal bacterial components, gut epithelia need to activate regulatory machinery to maintain epithelial homeostasis. Activating transcription factor 3 (ATF3) is a representative regulator in the negative feedback loop that modulates TLR-associated inflammatory responses. In the current study, the regulatory effects of ribosomal stress-induced ATF3 on Nod2-stimulated proinflammatory signals were assessed. Ribosomal inactivation caused persistent ATF3 expression that in turn suppressed proinflammatory chemokine production facilitated by Nod2. Decreased chemokine production was due to attenuation of Nod2-activated NF-κB and early growth response protein 1 (EGR-1) signals by ATF3. However, the underlying molecular mechanisms involve two convergent regulatory pathways. Although ATF3 induced by ribosomal inactivation regulated Nod2-induced EGR-1 expression epigenetically through the recruitment of histone deacetylase 1, NF-κB regulation was associated with posttranscriptional regulation by ATF3 rather than epigenetic modification. ATF3 induced by ribosomal inactivation led to the destabilization of p65 mRNA caused by nuclear entrapment of transcript-stabilizing human Ag R protein via direct interaction with ATF3. These findings demonstrate that ribosomal stress-induced ATF3 is a critical regulator in the convergent pathways between EGR-1 and NF-κB, which contributes to the suppression of Nod2-activated proinflammatory gene expression.

Selective inhibition of the master regulator transcription factor Egr-1 with catalytic oligonucleotides reduces myocardial injury and improves left ventricular systolic function in a preclinical model of myocardial infarction

BACKGROUND

Egr-1 is implicated in the pathogenesis of myocardial ischemia-reperfusion injury. The aim of this study was to ascertain the effectiveness of intracoronary delivery of DNAzyme targeting the transcription factor Egr-1 at reperfusion following experimental myocardial ischemia.

METHODS AND RESULTS

Functional DNAzyme targeting Egr-1 or a size-matched scrambled control were delivered via the intracoronary route immediately on reperfusion after 60 minutes' balloon occlusion of the left anterior descending coronary artery in a pig model of myocardial I/R injury (n=7 per treatment group). Heart function and extent of myocardial infarction were determined following intervention by echocardiography and cardiac magnetic resonance imaging, respectively. Hearts were removed and examined for molecular and histological markers of inflammation and apoptosis. Administration of functional DNAzyme led to an overall decrease in the expression of inflammatory markers including intracellular adhesion molecule-1, tissue factor, and complement 3, with associated decreases in the extent of neutrophil infiltration, oxidative damage, and subsequent apoptosis within the infarct border zone. Functional significance was indicated by an increase in salvaged left ventricular myocardium (P=0.012), ejection fraction (P=0.002), and fractional area change (P=0.039) in the functional DNAzyme-treated group compared with the control.

CONCLUSIONS

Egr-1 silencing through intracoronary delivery of a targeting DNAzyme at the time of reperfusion following acute myocardial ischemia decreases myocardial inflammation and apoptosis leading to improved cardiac function.

Interplay between EGR1 and SP1 is critical for 13-cis retinoic acid-mediated transcriptional repression of angiotensin type 1A receptor

Recently, we have demonstrated that 13-cis retinoic acid (13cRA) downregulates rat angiotensin type 1A receptor (Agtr1a) gene transcription through a MAP kinase (ERK1/2)-dependent mechanism in rat liver epithelial and aortic smooth muscle cells. However, the exact mechanism remained unknown. In this study, we determined the signaling intermediates activated by ERK1/2 involved in 13cRA-mediated Agtr1a downregulation. Rat Agtr1a chloramphenicol acetyltransferase (CAT) promoter construct containing a sequence -2541 and -1836 bp upstream of the start site demonstrated reduced CAT activity; this region possesses a specificity protein 1 (SP1) consensus sequence (5'-TGGGGCGGGGCGGGG-3'). Mobility shift analysis using untreated nuclear extracts in the presence of mithramycin A suggests that the trans-acting factor binding to this cis-acting element is SP1. 13cRA significantly reduced specific binding without any change in SP1 protein expression. Studies showed that 13cRA treatment maximally phosphorylates ERK1/2 within 5-10 min, which translocates to the nucleus, activating early growth response protein 1 (Egr1) mRNA expression at 20 min followed by de novo protein synthesis, leading to an EGR1/SP1 interaction. siRNA silencing of Egr1 restored Agtr1a mRNA and protein expression in 13cRA-treated cells, and Sp1 silencing results in complete loss of Agtr1a expression. Our study suggests that 13cRA-mediated activation of ERK1/2, through EGR1, is capable of disrupting SP1, the requisite trans-activator for Agtr1a expression, providing a novel paradigm in Agtr1a gene transcription.

Impact of prolonged cold preservation on the graft function and gene expression levels in an experimental lung transplantation model

PURPOSE

Ischemia reperfusion injury (IRI) remains a significant cause of morbidity and mortality after lung transplantation. Early growth response-1 (EGR1) drives the expression of inflammatory mediators and has an important role in IRI. We hypothesized that the severe IRI caused by a long preservation induces a specific expression pattern of EGR1 and its target genes which would correlate with the lung graft function.

METHODS

SD rat lungs were preserved at 4 °C for 3 or 18 h, then transplanted and reperfused. Pulmonary grafts were evaluated for the blood gas oxygenation and pathological findings. The intra-graft mRNA levels of EGR1 and its downstream target genes were measured by real-time PCR. A Western blotting analysis of the EGR1 expression was used to validate the changes in the protein level.

RESULTS

There was upregulation of EGR1, MIP-2 and PAI-1 when there was prolonged hypothermic preservation. The expression levels of MIP-2 and PAI-1 were observed to increase for up to 4 h in the 18 h preserved lungs. There were no differences in the expression levels of IL-1β and ICAM-1 between the lungs subjected to short and long periods of ischemia.

CONCLUSIONS

Our data showed that prolonged hypothermic graft preservation deteriorates the pulmonary graft function, which was associated with the induction of EGR1 and its downstream target genes, which may aggravate IRI following lung transplantation.

Egr1: a novel target for ameliorating acute allograft rejection in an experimental lung transplant model

OBJECTIVES

Acute allograft rejection is one of the significant complications occurring in lung transplant recipients. Early growth response-1 (Egr-1), zinc-finger-type transcription factor, is known as a master switch regulator of diverse chemical mediators. We used an orthotopic mouse model of left lung transplant to elucidate the function of Egr-1 in acute pulmonary rejection.

METHODS

Left lung grafts retrieved from C57BL/6 wild mice or C57BL/6 Egr-1-null mice were orthotopically transplanted into BALB/c mice; the lungs were harvested at day 1, 3, 5 or 7 after lung transplantation. The grade of acute rejection was histopathologically evaluated. The intragraft gene expression levels of Egr-1 and downstream target mediators were quantitatively measured by real-time polymerase chain reaction. Immunohistochemical analysis was used to determine the location and distribution of the Egr-1 protein in the pulmonary graft.

RESULTS

Severe acute rejection was observed in allografts from wild-type mice at 5 days after transplantation. Only minimal rejection was seen in the lung graft from Egr-1-null donor mice at 5 days after transplantation. Strong upregulation of Egr-1 mRNA transcripts was observed at day 1, which then decreased during the next 5 days. The mRNA of Egr-1 target mediators [interleukin-1-beta (IL-1β), monocyte chemotactic protein-1 (MCP-1) and plasminogen activator inhibitor-1] reached maximal levels at day 5. Egr-1-null allografts exhibited significantly lower expressions of IL-1β and MCP-1 mRNA (P < 0.05).

CONCLUSIONS

Our study showed that deletion of Egr-1 in lung allografts ameliorates severe acute rejection with the reduction of expression levels of chemical mediators, implying a new possible strategy for treating acute pulmonary allograft rejection.

Paradoxical exacerbation of neuronal injury in reperfused stroke despite improved blood flow and reduced inflammation in early growth response-1 gene-deleted mice

OBJECTIVES

Early growth response gene-1 (Egr-1) coordinates the rapid upregulation of diverse inflammatory and coagulation-related genes following ischemia/reperfusion. Genetic deletion of Egr-1 results in attenuated post-ischemic injury in diverse tissue systems. In the present study, we utilized a murine model of transient middle cerebral artery occlusion to probe the functional effects of Egr-1 deletion following cerebral ischemia/reperfusion.

METHODS

The time course of Egr-1 expression was established by Northern/Western blot analysis, and immunocytochemistry localized Egr-1 to specific cell populations. Flow cytometry was then employed to characterize the ischemic cellular infiltrate of both wild-type (+/+) and Egr-1-null (-/-) mice. Next, the functional effect of Egr-1 deletion was investigated in Egr-1-deficient mice and their wild-type littermates subjected to middle cerebral artery occlusion. Infarct volumes, neurological scores, and reperfusion cerebral blood flow were compared between cohorts.

RESULTS

Rapid upregulation of Egr-1 was observed in the ischemic hemisphere, and localized primarily to neurons and mononuclear cells. Egr-1 deletion led to a suppression of infiltrating neutrophils and activated microglia/macrophages (P<0.001). Additionally, although Egr-1 deletion enhanced post-ischemic cerebral blood flow, Egr-1-deficient mice suffered larger infarcts (P=0.01) and demonstrated a trend towards worse neurological scores (P=0.06) than wild-type controls.

DISCUSSION

Despite a reduction in the proportion of infiltrating inflammatory cells/activated microglia and improvement in post-ischemic reperfusion, Egr-1-deficient animals suffer larger infarcts in our model. Therefore, cerebral Egr-1 expression may function to protect neurons despite its adverse modulatory consequences for inflammation and thrombosis.

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.

CCR2 regulates monocyte recruitment as well as CD4 T1 allorecognition after lung transplantation

Graft rejection remains a formidable problem contributing to poor outcomes after lung transplantation. Blocking chemokine pathways have yielded promising results in some organ transplant systems. Previous clinical studies have demonstrated upregulation of CCR2 ligands following lung transplantation. Moreover, lung injury is attenuated in CCR2-deficient mice in several inflammatory models. In this study, we examined the role of CCR2 in monocyte recruitment and alloimmune responses in a mouse model of vascularized orthotopic lung transplantation. The CCR2 ligand MCP-1 is upregulated in serum and allografts following lung transplantation. CCR2 is critical for the mobilization of monocytes from the bone marrow into the bloodstream and for the accumulation of CD11c(+) cells within lung allografts. A portion of graft-infiltrating recipient CD11c(+) cells expresses both recipient and donor MHC molecules. Two-photon imaging demonstrates that recipient CD11c(+) cells are associated with recipient T cells within the graft. While recipient CCR2 deficiency does not prevent acute lung rejection and is associated with increased graft infiltration by T cells, it significantly reduces CD4(+) T(h)1 indirect and direct allorecognition. Thus, CCR2 may be a potential target to attenuate alloimmune responses after lung transplantation.

Protective effect of carbon monoxide pre-conditioning on LPS-induced endothelial cell stress

Increasing evidence indicates that carbon monoxide (CO) may protect against several diseases including sepsis. The ability of CO pre-treatment to provide good pre-conditioning against lipopolysaccharide (LPS)-induced injury was tested using an in vitro model of primary culture of porcine aortic endothelial cells (pAEC). pAEC were exposed to CO (250 ppm) or air for 1 h prior to the addition of LPS (10 microg/ml). Hsp70, HO-1, and Egr-1 protein levels were determined as well as vascular endothelial growth factor (VEGF) secretion after 4, 7, and 15 h. The effect of CO on LPS-induced apoptosis was also detected at 15 h. CO pre-treatment before the addition of LPS, significantly reduced LPS-induced apoptosis. LPS induced an increase in the level of VEGF in culture media after 7 and 15 h, and a larger increase was detected in CO pre-treated cells. In addition, CO pre-treatment reduced LPS-induced Hsp70, HO-1, and Egr-1 protein expression. In conclusion, CO treatment seems to provide a good pre-conditioning for the prevention of LPS-induced endothelial injury.

N-n-butyl haloperidol iodide protects cardiac microvascular endothelial cells from hypoxia/reoxygenation injury by down-regulating Egr-1 expression

AIMS

Our previous studies have shown that N-n-butyl haloperidol iodide (F2) can antagonize myocardial ischemia/reperfusion (I/R) injury by down-regulating the early growth response (Egr)-1 expression, but the molecular mechanisms are not well understood. Because there is evidence implicating myocardial I/R injury is closely associated with endothelial dysfunction. The present study is to test the hypothesis that the protective effects of F2 on myocardial I/R injury is related closely with down-regulating Egr-1 expression on cardiac microvascular endothelial cells (CMECs).

METHODS

A model of cultured CMECs exposed to hypoxia/reoxygenation (H/R) was developed. With antisense Egr-1 oligodeoxyribonucleotide (ODN), the relationship between Egr-1 expression and endothelial H/R injury was investigated. Egr-1 mRNA and protein expression were examined by real-time fluorescent quantitative PCR, immunocytochemical staining and Western-blot analysis. Lactate dehydrogenase (LDH), malondialdehyde (MDA), superoxide dismutase (SOD), intercellular adhesion molecule-1 (ICAM-1), adherence of neutrophil and platelets, and cell viability were measured after H/R to evaluate the degree of endothelial injury.

RESULTS

Pretreatment with antisense Egr-1 ODN significantly reduced Egr-1 protein expression and attenuated injury of CMECs. Consistent with down-regulation of Egr-1 expression by F2, inflammation and other damage were significantly reduced as evidenced by a decrease of ICAM-1 expression, reduction of neutrophil and platelets adherence, increase in SOD, and decreases in MDA and LDH levels, resulting in the rise of cell viability.

CONCLUSIONS

We demonstrate a protective effect of F2 in CMECs against H/R injury by down-regulating Egr-1 expression, which might be play a vital role in the pathogenesis of myocardial I/R injury.

Association of early growth response-1 gene polymorphisms with total IgE and atopy in asthmatic children

Early growth response-1 (Egr-1) is expressed in human airways and found to modulate tumor necrosis factor, immunoglobulin E (IgE), airway responsiveness, and interleukin-13-induced inflammation in mice. We investigated the effects of Chinese-tagging single nucleotide polymorphisms (SNPs) of Egr-1 on asthma traits in 298 Chinese asthmatic children and 175 controls, and a replication community cohort of 191 controls. Tag SNP (-4071 A-->G) and three additional SNPs (-1427 C-->T, -151 C-->T and IVS1 -42 C-->T) were genotyped by restriction fragment length polymorphism (RFLP). Significant associations were found between plasma total IgE concentration and -4071 A-->G (p = 0.008) and IVS1 -42 C-->T (p = 0.027) in asthmatic patients. After Bonferroni correction, only -4071 A-->G showed significant association. Multivariate regression analysis confirmed this significant association with a standardized coefficient beta of 0.156 (95% CI: 0.046-0.317; p = 0.009) in asthmatics among the three SNPs with age and gender-adjusted. In -4071 A-->G, IgE(log) was significantly higher in patients with the GG genotype than the AA genotype (p = 0.009). In addition, -4071 A-->G was significantly associated with atopy (p = 0.016) and high total IgE concentration (p = 0.030) among asthmatics. Patients with the G allele had a 3.5-fold risk of having atopy and a 2.0-fold risk of having high total IgE concentration than those homozygous for the A allele. This is the first report to show significant association of Egr-1 polymorphisms with plasma total IgE and atopy in asthmatics. It may help to explore the pharmacogenetics of Egr-1 inhibitors.

Transcriptional regulation of EGR-1 by the interleukin-1-JNK-MKK7-c-Jun pathway

The proinflammatory cytokine interleukin (IL)-1 activates several hundred genes within the same cell. This occurs in part by activation of the MKK7-JNK-c-Jun signaling pathway whose precise role in the regulation of individual inflammatory genes is still incompletely understood. To identify the genes that are under specific control of activated JNK, we used a JNK-MKK7 fusion protein. Genome-wide microarray analysis revealed EGR-1 as the transcript that was most strongly induced by JNK-MKK7. IL-1-stimulated EGR-1 mRNA and protein expression were impaired in cells lacking JNK or c-Jun. Transcriptional activation of the EGR-1 promoter by JNK-MKK7 or by IL-1 required a single upstream AP-1 site and three distal serum-response elements (SRE). Reconstitution experiments in c-Jun-deficient cells revealed that c-Jun is required for EGR-1 transcription through both the AP-1 site and the distal SREs. By chromatin immunoprecipitation analysis, we found IL-1-inducible recruitment of c-Jun to the AP-1 site and to the region containing the three distal SREs. These experiments suggest that c-Jun plays a dual role in EGR-1 transcription. It directly binds to the AP-1 element, and at the same time it is essential for promoter activation through the three distal SREs by an indirect unknown mechanism. As predicted by TRANSFAC analysis and verified by ChIP experiments, IL-1-induced EGR-1 protein binds to the promoter regions of inflammatory mediators such as IL-6, IL-8, and CCL2. Furthermore, short interfering RNA-mediated suppression of EGR-1 partially suppresses IL-1-inducible transcription of IL-8, IL-6, and CCL2. In summary, we provide novel evidence for a complex c-Jun-mediated mechanism that is essential for inducible EGR-1 expression. We identify this pathway as a previously unrecognized part of a multistep gene regulatory network that controls cytokine and chemokine expression via the IL-1-MKK7-JNK-c-Jun-EGR-1 pathway.

Transcription factor early growth response-1 induction mediates inflammatory gene expression and brain damage following transient focal ischemia

Early growth response-1 (Egr1) is a sequence-specific transcription factor (TF) which is induced under hypoxic conditions. We presently report that transient middle cerebral artery occlusion (MCAO) leads to increased expression of Egr1 in the brains of adult mice and rats between 2 h and 5 days of reperfusion with a peak increase of 8-12-fold at 1 day. When subjected to transient MCAO and 3 days of reperfusion, Egr1-/- mice showed significantly smaller infarcts (by 44.9 +/- 8.4%, p < 0.05) and improved neurological function than Egr1+/+ littermates. Following transient MCAO, brains of Egr1-/- mice showed less water accumulation and decreased neutrophil infiltration (by 42 +/- 8%, p < 0.05) compared to Egr1+/+ mice. The number of activated microglia/macrophages were also significantly lower (OX42+ cells by 53 +/- 9%, p < 0.05 and ED1+ cells by 59 +/- 11%) in the post-ischemic cortex of Egr1-/- mice compared to Egr1+/+ mice. In addition, post-ischemic inflammatory gene expression was less pronounced in the brains of Egr1-/- mice compared to Egr1+/+ mice. Preventing cerebral Egr1 protein induction with small interference RNAs that target Egr1 decreased inflammatory gene expression and led to smaller infarcts (by 40.2 +/- 6.9%, p < 0.05) and reduced neurological deficits in rats subjected to transient MCAO. Conversely, transient MCAO following adenoviral-mediated Egr1 over-expression exacerbated the infarct volume (by 29 +/- 5.3%, p < 0.05) and worsened the neurological deficits in rats. These studies indicate Egr1 as a significant contributor of inflammation and neuronal damage after stroke.

The protective effects of N-n-butyl haloperidol iodide on myocardial ischemia-reperfusion injury in rats by inhibiting Egr-1 overexpression

AIMS

Our previous studies have shown that N-n-butyl haloperidol iodide (F(2)) can antagonize myocardial ischemia/reperfusion (I/R) injury by blocking intracellular Ca(2+) overload. The present study is to test the hypothesis that the protective effects of F(2) on myocardial I/R injury is mediated by downregulating Egr-1 expression.

METHODS

The Sprague-Dawley rat myocardial I/R model and cardiomyocyte hypoxia/reoxygenation (H/R) model were established. With antisense Egr-1 oligodeoxyribonucleotide (ODN), the relationship between Egr-1 expression and myocardial I/R injury was investigated. Hemodynamic parameters, myeloperoxidase (MPO), cardiac troponin I (cTnI) and tumor necrosis factor-alpha (TNF-alpha) were measured to assess the degree of injury and inflammation of myocardial tissues and cells. Egr-1 mRNA and protein expressions were examined by Northern-blot and Western-blot analyses.

RESULTS

Treatment with antisense Egr-1 ODN significantly reduced Egr-1 protein expression and attenuated injury of myocardial tissues and cells. Meanwhile, treatment with F(2) significantly inhibited the overexpression of Egr-1 mRNA and protein in myocardial tissues and cells. Consistent with downregulation of Egr-1 expression by F(2), inflammation and other damages were significantly relieved evidenced by the amelioration of hemodynamics, the reduction in myocardial MPO activity as well as the decrease in leakage of cTnI and release of TNF-alpha from cardiomyocyte.

CONCLUSIONS

These results suggested that the overexpression of Egr-1 was causative in myocardial I/R or H/R injury, and F(2) could protect myocardial tissues and cells from I/R or H/R injury, which was largely due to the inhibition of Egr-1 overexpression.

Ozone induces oxidative stress in rat alveolar type II and type I-like cells

Ozone is a highly reactive gas present in urban air, which penetrates deep into the lung and causes lung injury. The alveolar epithelial cells are among the first cell barriers encountered by ozone. To define the molecular basis of the cellular response to ozone, primary cultures of rat alveolar type II and type I-like cells were exposed to 100 ppb ozone or air for 1 h. The mRNA from both phenotypes was collected at 4 and 24 h after exposure for gene expression profiling. Ozone produced extensive alterations in gene expression involved in stress and inflammatory responses, transcription factors, antioxidant defenses, extracellular matrix, fluid transport, and enzymes of lipid metabolism and cell differentiation. Real-time reverse transcription-polymerase chain reaction and Western blot analysis verified changes in mRNA and protein levels of selected genes. Besides the increased stress response, ozone exposure downregulated genes of cellular differentiation. The changes were more prominent at 4 h in the type I-like phenotype and at 24 h in the type II phenotype. The type I-like cells were more sensitive to ozone than type II cells. The genome-wide changes observed provide insight into signal pathways activated by ozone and how cellular protection mechanisms are initiated.

Effects of N-n-butyl haloperidol iodide on myocardial ischemia/reperfusion injury and Egr-1 expression in rat

We have previously shown that N-n-butyl haloperidol iodide (F2) derived from haloperidol reduces ischemia/reperfusion-induced myocardial injury by blocking intracellular Ca2+ overload. This study tested the hypothesis that cardio-protection with F2 is associated with an attenuation in the expression of early growth response gene 1 (Egr-1). In an in vivo rat model of 60 min coronary occlusion followed by 180 min of reperfusion, treatment with F2 significantly reduced myocardial injury evidenced by the reduction in release of plasma creatine kinase, myocardial creatine kinase isoenzyme and lactate dehydrogenase. In cultured neonatal rat cardiomyocytes of hypoxia for 3 h and reoxygenation for 1 h, F2 treatment attenuated necrotic and apoptotic cell death, as demonstrated by electron microscopy. Concomitant with cardio-protection by F2, the increased expression levels of Egr-1 mRNA and protein were significantly reduced in myocardial tissue and cultured cardiomyocytes as detected by reverse transcription-polymerase chain reaction, immunohistochemistry and immunocytochemistry. In conclusion, these results suggest that the protective effect of F2 on ischemia/reperfusion- or hypoxia/reoxygenation-induced myocardial injury might be partly mediated by downregulating Egr-1 expression.

Carbon monoxide rescues ischemic lungs by interrupting MAPK-driven expression of early growth response 1 gene and its downstream target genes

Carbon monoxide (CO), an endogenous cytoprotective product of heme oxygenase type-1 regulates target thrombotic and inflammatory genes in ischemic stress. Regulation of the gene encoding early growth response 1 (Egr-1), a potent transcriptional activator of deleterious thrombotic and inflammatory cascades, may govern CO-mediated ischemic lung protection. The exact signaling mechanisms underlying CO-mediated cytoprotection are not well understood. In this study we tested the hypothesis that inhibition of mitogen-activated protein kinase-dependent Egr-1 expression may be pivotal in CO-mediated ischemic protection. In an in vivo isogeneic rat lung ischemic injury model, inhaled CO not only diminished fibrin accumulation and leukostasis and improved gas exchange and survival but also suppressed extracellular signal-regulated kinase (ERK) activation, Egr-1 expression, and Erg DNA-binding activity in lung tissue. Additionally, CO-mediated inhibition of Egr-1 reduced expression of target genes, such as tissue factor, serpine-1, interleukin-1, and TNF-alpha. However, CO failed to inhibit serpine-1 expression after unilateral lung ischemia in mice null for the Egr-1 gene. In RAW macrophages in vitro, hypoxia-induced Egr-1 mRNA expression was ERK-dependent, and CO-mediated suppression of ERK activation resulted in Egr-1 inhibition. Furthermore, CO suppression of ERK phosphorylation was reversed by the guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one but was insensitive to cAMP-dependent protein kinase A inhibition with H89 and NO synthase inhibition with l-nitroarginine methyl ester. This finding indicates that CO suppresses ERK in a cGMP-dependent but cAMP/protein kinase A- and NO-independent manner. Together, these data identify a unifying molecular mechanism by which CO interrupts proinflammatory and prothrombotic mediators of ischemic injury.

Early growth response-1 in cardiovascular pathobiology

The immediate-early gene product and zinc finger transcription factor early growth response (Egr)-1 plays a key master regulatory role in multiple cardiovascular pathological processes. This article reviews the amazing recent evidence implicating Egr-1 in atherosclerosis, intimal thickening after acute vascular injury, ischemic pathology, angiogenesis, allograft rejection, and cardiac hypertrophy.

Unique gene expression and hepatocellular injury in the lipopolysaccharide-ranitidine drug idiosyncrasy rat model: comparison with famotidine

Rats cotreated with lipopolysaccharide (LPS) and ranitidine (RAN) but not LPS and famotidine (FAM) develop hepatocellular injury in an animal model of idiosyncratic drug reactions. Evaluation of liver gene expression in rats given LPS and/or RAN led to confirmation that the hemostatic system, hypoxia, and neutrophils (PMNs) are critical mediators in LPS/RAN-induced liver injury. We tested the hypothesis that unique gene expression changes distinguish LPS/RAN-treated rats from rats given LPS or RAN alone and from those cotreated with LPS/FAM. Rats were treated with a nonhepatotoxic dose of LPS (44.4 x 10(6) endotoxin units/kg, iv) or its vehicle. Two hours thereafter they were given RAN (30 mg/kg, iv), FAM (either 6 mg/kg, a pharmacologically equi-efficacious dose, or 28.8 mg/kg, an equimolar dose, iv), or vehicle. They were killed 2 or 6 h after drug treatment for evaluation of hepatotoxicity (2 and 6 h) and liver gene expression (2 h only). At a time before the onset of hepatocellular injury, hierarchical clustering distinguished rats treated with LPS/RAN from those given LPS alone. 205 probesets were expressed differentially to a greater or lesser degree only in LPS/RAN-treated rats compared to LPS/FAM or LPS alone, which did not develop liver injury. These included VEGF, EGLN3, MAPKAPK-2, BNIP3, MIP-2, COX-2, EGR-1, PAI-1, IFN-gamma, and IL-6. Expression of these genes was confirmed by real-time PCR. Serum concentrations of MIP-2, PAI-1, IFN-gamma, and IL-6 correlated with their respective gene expression patterns. Overall, the expression of several gene products capable of controlling requisite mediators of injury (i.e., hemostasis, hypoxia, PMNs) in this model were enhanced in livers of LPS/RAN-treated rats. Furthermore, enhanced expression of MAPKAPK-2 in RAN-treated rats and its target genes in LPS/RAN-treated rats suggests that p38/MAPKAPK-2 signaling is a regulation point for enhancement of LPS-induced gene expression by RAN.

Hypoxic preconditioning protects against ischemic brain injury

Animals exposed to brief periods of moderate hypoxia (8% to 10% oxygen for 3 hours) are protected against cerebral and cardiac ischemia between 1 and 2 days later. This hypoxia preconditioning requires new RNA and protein synthesis. The mechanism of this hypoxia-induced tolerance correlates with the induction of the hypoxia-inducible factor (HIF), a transcription factor heterodimeric complex composed of inducible HIF-1alpha and constitutive HIF-1beta proteins that bind to the hypoxia response elements in a number of HIF target genes. Our recent studies show that HIF-1alpha correlates with hypoxia induced tolerance in neonatal rat brain. HIF target genes, also induced following hypoxia-induced tolerance, include vascular endothelial growth factor, erythropoietin, glucose transporters, glycolytic enzymes, and many other genes. Some or all of these genes may contribute to hypoxia-induced protection against ischemia. HIF induction of the glycolytic enzymes accounts in part for the Pasteur effect in brain and other tissues. Hypoxia-induced tolerance is not likely to be equivalent to treatment with a single HIF target gene protein since other transcription factors including Egr-1 (NGFI-A) have been implicated in hypoxia regulation of gene expression. Understanding the mechanisms and genes involved in hypoxic tolerance may provide new therapeutic targets to treat ischemic injury and enhance recovery.

Lung transplantation: opportunities for research and clinical advancement

Lung transplantation is the only definitive therapy for many forms of end-stage lung diseases. However, the success of lung transplantation is limited by many factors: (1) Too few lungs available for transplantation due to limited donors or injury to the donor lung; (2) current methods of preservation of excised lungs do not allow extended periods of time between procurement and implantation; (3) acute graft failure is more common with lungs than other solid organs, thus contributing to poorer short-term survival after lung transplant compared with that for recipients of other organs; (4) lung transplant recipients are particularly vulnerable to pulmonary infections; and (5) chronic allograft dysfunction, manifest by bronchiolitis obliterans syndrome, is frequent and limits long-term survival. Scientific advances may provide significant improvements in the outcome of lung transplantation. The National Heart, Lung, and Blood Institute convened a working group of investigators on June 14-15, 2004, in Bethesda, Maryland, to identify opportunities for scientific advancement in lung transplantation, including basic and clinical research. This workshop provides a framework to identify critical issues related to clinical lung transplantation, and to delineate important areas for productive scientific investigation.

Curcumin, the active constituent of turmeric, inhibits amyloid peptide-induced cytochemokine gene expression and CCR5-mediated chemotaxis of THP-1 monocytes by modulating early growth response-1 transcription factor

Epidemiological studies show reduced risk of Alzheimer's disease (AD) among patients using non-steroidal inflammatory drugs (NSAID) indicating the role of inflammation in AD. Studies have shown a chronic CNS inflammatory response associated with increased accumulation of amyloid peptide and activated microglia in AD. Our previous studies showed that interaction of Abeta1-40 or fibrilar Abeta1-42 caused activation of nuclear transcription factor, early growth response-1 (Egr-1), which resulted in increased expression of cytokines (TNF-alpha and IL-1beta) and chemokines (MIP-1beta, MCP-1 and IL-8) in monocytes. We determined whether curcumin, a natural product known to have anti-inflammatory properties, suppressed Egr-1 activation and concomitant expression of cytochemokines. We show that curcumin (12.5-25 microm) suppresses the activation of Egr-1 DNA-binding activity in THP-1 monocytic cells. Curcumin abrogated Abeta1-40-induced expression of cytokines (TNF-alpha and IL-1beta) and chemokines (MIP-1beta, MCP-1 and IL-8) in both peripheral blood monocytes and THP-1 cells. We found that curcumin inhibited Abeta1-40-induced MAP kinase activation and the phosphorylation of ERK-1/2 and its downstream target Elk-1. We observed that curcumin inhibited Abeta1-40-induced expression of CCR5 but not of CCR2b in THP-1 cells. This involved abrogation of Egr-1 DNA binding in the promoter of CCR5 by curcumin as determined by: (i) electrophoretic mobility shift assay, (ii) transfection studies with truncated CCR5 gene promoter constructs, and (iii) chromatin immunoprecipitation analysis. Finally, curcumin inhibited chemotaxis of THP-1 monocytes in response to chemoattractant. The inhibition of Egr-1 by curcumin may represent a potential therapeutic approach to ameliorate the inflammation and progression of AD.

Egr-1 antisense oligonucleotides inhibit hypoxia-induced proliferation of pulmonary artery adventitial fibroblasts

In most mammalian species, chronic exposure to hypoxia leads to pulmonary hypertension and vascular remodeling. The adventitial fibroblast, because of its ability to proliferate in response to hypoxia, is thought to be a critical cell in the remodeling process. However, the transcription factors driving hypoxia-induced fibroblast proliferation have yet to be elucidated. The early growth response-1 (Egr-1) transcription factor has been shown to be upregulated by hypoxia in pulmonary artery adventitial fibroblasts. We therefore hypothesized that Egr-1 is directly involved in hypoxia-induced adventitial fibroblast proliferation. Immunohistochemical analysis of in vivo lung tissue from animals exposed to chronic hypoxia revealed increased expression of Egr-1 in the pulmonary artery fibroblasts vs. expression shown in normoxic controls. In fibroblasts cultured from chronically hypoxic animals, exposure to 1% oxygen upregulated Egr-1 protein and cell proliferation. To evaluate the role of Egr-1 in hypoxia-induced proliferation, we employed an Egr-1 antisense strategy. Addition of antisense Egr-1 oligonucleotides, but not sense oligonucleotides, attenuated the hypoxia-induced upregulation of Egr-1 protein and reduced hypoxia-induced DNA synthesis by 50%. Cell proliferation was also significantly inhibited by the addition of antisense Egr-1 oligonucleotides but not the sense oligonucleotides. In addition, hypoxia-induced upregulations of cyclin D and epidermal growth factor receptor were attenuated by Egr-1 antisense oligonucleotides. We conclude that Egr-1 protein expression is very sensitive to upregulation by hypoxia in pulmonary artery adventitial fibroblasts and that it plays an important role in the autonomous growth phenotype induced by hypoxia in these cells.

Decreased expression of early growth response-1 and its role in uterine leiomyoma growth

Expression of early growth response (Egr)-1, a transcriptional factor implicated in growth regulation, is suppressed in several malignant tumors. The present study investigated the expression of Egr-1 and related genes in uterine leiomyoma and normal myometrium to determine possible contributions of Egr-1 to neoplastic growth in leiomyoma cells. Levels of Egr-1 transcripts were decreased in all leiomyomas (n = 20) to approximately 10% of levels in corresponding myometrium, where basal expression was high. Preoperative leuprorelin acetate therapy increased levels of Egr-1 mRNA in normal myometrium only. Northern blot analysis using additional sample sets (n = 5) revealed the full-length Egr-1 transcript. Western blot analysis (n = 5) confirmed decreased expression of Egr-1 protein. Southern blot analysis of the Egr-1 gene and microsatellite analysis of the chromosomal location at 5q31 (D5S414, D5S500, and D5S476) revealed neither DNA recombination nor loss of heterozygosity in leiomyomas. Moreover, Egr-1 retained identical responsiveness to phorbol 12-myristate 13-acetate in primary cultures derived from both leiomyoma and normal tissues. Electrophoretic mobility shift analysis revealed that phorbol 12-myristate 13-acetate-induced Egr-1 in leiomyoma cells retained DNA binding ability. Egr-1 thus appears functionally intact in leiomyoma cells. Finally, consistent with the role of Egr-1 in growth inhibition, transfection of Egr-1 expression vector into a myometrial cell line (KW) that expresses low levels of Egr-1 and displays rapid growth inhibited thymidine uptake in these cells. Egr-1 may display tumor-suppressing activity and offers a potential target for leiomyoma management.

FK 409 ameliorates small-for-size liver graft injury by attenuation of portal hypertension and down-regulation of Egr-1 pathway

OBJECTIVE

To investigate whether low-dose nitric oxide donor FK 409 could attenuate small-for-size graft injury in liver transplantation using small-for-size grafts.

SUMMARY BACKGROUND DATA

The major concern of live donor liver transplantation is small-for-size graft injury at the early phase after transplantation. Novel therapeutic strategies should be investigated.

METHODS

We employed a rat orthotopic liver transplantation model using small-for-size (40%) graft. FK 409 was given at 30 minutes before graft harvesting (2 mg/kg) to the donor and immediately after reperfusion (1 mg/kg) to the recipient (FK group). Graft survival, intragraft genes expression, portal hemodynamics, and hepatic ultrastructural changes were compared between the 2 groups.

RESULTS

Seven-day graft survival rates in the FK group were significantly improved compared with those of rats not receiving FK 409 (control group; 80% versus 28.6%, P = 0.018). In the FK group, portal pressure was significantly decreased within the first 60 minutes after reperfusion whereas in the control group, transient portal hypertension was observed. Intragraft expression (both mRNA and protein) of early growth response-1, endothelin-1, endothelin-1 receptor A, tumor necrosis factor-alpha, macrophage-inflammatory protein-2, and inducible nitric oxide synthase was significantly down-regulated accompanied with up-regulation of heme oxygenase-1, A20, interferon-gamma-inducible protein-10, and interleukin-10 during the first 24 hours after reperfusion. Hepatic ultrastructure, especially the integrity of sinusoids was well protected in the FK group.

CONCLUSIONS

Low-dose FK 409 rescues small-for-size grafts in liver transplantation by attenuation of portal hypertension and amelioration of acute phase inflammatory response by down-regulation of Egr-1, together with prior induction of heat shock proteins.

Induction of early growth-response factor 1 by platelet-derived growth factor in human airway smooth muscle

Platelet-derived growth factors (PDGF) may contribute to the activation and growth of smooth muscle that is characteristic of airway remodeling in asthmatic patients. Early growth response 1 (EGR-1) is a transcription factor that is induced in several cell types by PDGF and may mediate some of the effects of PDGF. We show that human airway smooth muscle cells in cell culture express EGR-1 1 h after addition of PDGF. Analysis of the EGR-1 promoter indicates that a serum response element located between 663 and 654 bp 5' to the ATG start site is essential for this induction. Serum response factor, E26 transcription factor-like protein 1, and serum protein 1 bind to this region. PDGF causes phosphorylation of ERK1/2 and is temporally associated with E26 transcription factor-like protein 1 phosphorylation. Finally, the specific ERK1/2 inhibitor U-0126 abolishes PDGF-induced expression of EGR-1 in these cells. On the basis of these data, we speculated that EGR-1 would be increased in airway smooth muscle of asthmatic patients compared with nonasthmatic controls. Using immunohistochemistry, we found that EGR-1 protein was expressed in airway smooth muscle cells and epithelial cells of asthmatic patients and nonasthmatic controls; however, there was no significant difference in the intensity of staining between groups. EGR-1 was similarly expressed in the lungs of mice with and without ovalbumin-induced airway inflammation; however, there was no difference between groups by immunohistochemistry and quantitative PCR. Although EGR-1 is induced by PDGF in human airway smooth muscle cells in cell culture, the role of EGR-1 in airway remodeling and asthma remains to be established.

Antisense to the early growth response-1 gene (Egr-1) inhibits prostate tumor development in TRAMP mice

Egr-1 is a transcription factor induced by stress or injury, mitogens, and differentiation factors. Egr-1 regulates the expression of genes involved in growth control or survival. Expression of Egr-1 results in either promotion or regression of cell proliferation, depending on cell type and environment. Egr-1 acts as a tumor suppressor in many cell types and loss of Egr-1 has been proposed to contribute to cancer progression. There is strong new evidence however suggesting that Egr-1 overexpression is involved in prostate cancer progression. For example, Egr-1 expression levels are elevated in human prostate carcinomas in proportion to grade and stage. Furthermore, prostate cancer progression was significantly delayed in two models of prostate cancer mice lacking Egr-1. Our objective in the present study is to test whether inhibition of Egr-1 function would block cell proliferation and inhibit the transformed phenotype of prostate cancer cells in vitro and in vivo. We describe the development of high affinity and high specificity antisense oligonucleotides that efficiently inhibit Egr-1 expression. We show that inhibition of Egr-1 expression in mouse or human prostate cancer cells decreased proliferation and reduced the capacity of these cells to form colonies and to grow in soft agar. Conversely, stable expression of Egr-1 in normal human prostate epithelial 267B1 cells promoted transformation. In TRAMP mice, treatment with Egr-1 antisense oligonucleotides delayed the occurrence of prostate tumors. Importantly, Egr-1 antisense showed little or no toxicity when injected into animals. Finally, we identified a few genes such as cyclin D2, p19ink4d, and Fas that are directly regulated by Egr-1 in prostate cancer cells and that control cell cycle and survival.

Early Growth Response-1 Promotes Atherogenesis

Early growth response-1 (Egr-1) regulates expression of proinflammatory and procoagulant genes in acute cell stress. Experimental evidence suggested that Egr-1 transcripts were upregulated in human atherosclerotic plaques versus adjacent unaffected tissue. To test the impact of Egr-1 in chronic vascular stress, we examined its role in a murine model of atherosclerosis. Real-time PCR analysis of aortae retrieved from apoE −/− mice demonstrated increased Egr-1 transcripts in an age-dependent manner, compared with aortae retrieved from C57BL/6 control animals. Therefore, homozygous Egr-1 −/− mice were bred into the apoE −/− background. Homozygous double-knockout mice (Egr-1 −/− /apoE −/− ) in the C57BL/6 background were maintained on normal chow diet. At age 14 and 24 weeks, atherosclerotic lesion area and complexity at the aortic root were strikingly decreased in mice deficient in both Egr-1 and apoE compared with mice deficient in apoE alone. In parallel, transcripts for genes regulating the inflammatory/prothrombotic response were diminished in Egr-1 −/− /apoE −/− aortae versus apoE −/− . In vitro, oxidized low-density lipoprotein (OxLDL), a key factor inciting atherogenic mechanisms in the vasculature, upregulated Egr-1 expression in monocytes via the MEK-ERK1/2 pathway. We conclude that Egr-1 broadly regulates expression of molecules critically linked to atherogenesis and lesion progression.

Chemokine receptor-dependent alloresponses

Immunologists have typically viewed alloreactivity schematically as a function of antigen presentation, expansion of alloreactive T and B cells within regional lymphoid tissues, and cellular infiltration and destruction of an allograft. Actual details of the steps between immune activation and accumulation of effector cells within a graft typically have not received much attention. However, just how cells "know" to move to and migrate within a graft or not is proving to be of increasing interest, as the chemokine-dependent mechanisms underlying leukocyte recruitment to a transplant are dissected. Experimentally, chemokine receptor targeting can prolong or induce permanent allograft survival, despite preservation of alloresponses within secondary lymphoid tissues, whereas current immunosuppressive protocols have only modest effects on chemokine production and leukocyte homing. Recent knowledge of the chemokine-dependent nature of allograft rejection, acceptance, and tolerance induction are presented as a basis for understanding the rationale for preclinical trials of chemokine receptor-targeted therapies currently underway in primate recipients of solid organ allografts.

Chemokines and their receptors as markers of allograft rejection and targets for immunosuppression

Although almost every known chemokine and chemokine receptor is expressed at some stage during development of allograft rejection, mechanistic studies indicate that the actual key effector mechanisms are rather few. Thus, in vivo studies have alleviated concerns regarding possible biological redundancy and the pleiotropic effects of these molecules, and have resulted in a focus on CXCR3, CCR5 and their respective ligands as key mediators of host alloresponses, especially in acute rejection. Data are also accruing regarding the importance of chemokine/chemokine receptor pathways in ischemia/reperfusion, chronic rejection and tolerance induction following co-stimulation blockade, providing new targets for immune monitoring and therapeutic intervention.

Inhibition of Egr-1 expression reverses transformation of prostate cancer cells in vitro and in vivo

Transcription factor early growth response-1 (Egr-1) is a crucial regulator of cell growth, differentiation and survival. Several observations suggest that Egr-1 is growth promoting in prostate cancer cells and that blocking its function may impede cancer progression. To test this hypothesis, we developed phosphorothioate antisense oligonucleotides that efficiently inhibit Egr-1 expression without altering the expression of other family members Egr-2, Egr-3 and Egr-4. In TRAMP mouse-derived prostate cancer cell lines, our optimal antisense oligonucleotide decreased the expression of the Egr-1 target gene transforming growth factor-beta1 whereas a control oligonucleotide had no effect, indicating that the antisense blocked Egr-1 function as a transcription factor. The antisense oligonucleotide deregulated cell cycle progression and decreased proliferation of the three TRAMP cell lines by an average of 54+/-3%. Both colony formation and growth in soft agar were inhibited by the antisense oligonucleotide. When TRAMP mice were treated systemically for 10 weeks, the incidence of palpable tumors at 32 weeks of age in untreated mice or mice injected with the control scramble oligonucleotide was 87%, whereas incidence of tumors in antisense-Egr-1-treated mice was significantly reduced to 37% (P=0.026). Thus, Egr-1 plays a functional role in the transformed phenotype and may represent a valid target for prostate cancer therapy.

Pulmonary gene expression profiling of inhaled ricin

Aerosol exposure to ricin causes irreversible pathological changes of the respiratory tract resulting in epithelial necrosis, pulmonary edema and ultimately death. The pulmonary genomic profile of BALB/c mice inhalationally exposed to a lethal dose of ricin was examined using cDNA arrays. The expression profile of 1178 mRNA species was determined for ricin-exposed lung tissue, in which 34 genes had statistically significant changes in gene expression. Transcripts identified by the assay included those that facilitate tissue healing (early growth response gene (egr)-1), regulate inflammation (interleukin (IL)-6, tristetraproline (ttp)), cell growth (c-myc, cytokine-inducible SH2-containing protein (cish)- 3), apoptosis (T-cell death associated protein (tdag)51, pim-1) and DNA repair (ephrin type A receptor 2 (ephA2)). Manipulation of these gene products may provide a means of limiting the severe lung damage occurring at the cellular level. Transcriptional activation of egr-1, cish-3, c-myc and thrombospondin (tsp)-1 was already apparent when pathological and physiological changes were observed in the lungs at 12 h postexposure. These genes may well serve as markers for ricin-induced pulmonary toxicity. Ongoing studies are evaluating this aspect of the array data and the potential of several genes for clinical intervention.

Amyloid peptide-induced cytokine and chemokine expression in THP-1 monocytes is blocked by small inhibitory RNA duplexes for early growth response-1 messenger RNA

In Alzheimer's disease (AD) one finds increased deposition of A beta and also an increased presence of monocytes/macrophages in the vessel wall and activated microglial cells in the brain. AD patients show increased levels of proinflammatory cytokines by activated microglia. Here we used a human monocytic THP-1 cell line as a model for microglia to delineate the cellular signaling mechanism involved in amyloid peptides (A beta(1-40) and A beta(1-42))-induced expression of inflammatory cytokines and chemokines. We observed that A beta peptides at physiological concentrations (125 nM) increased mRNA expression of cytokines (TNF-alpha, and IL-1 beta) and chemokines (monocyte chemoattractant protein-1 (MCP-1), IL-8, and macrophage inflammatory protein-1 beta (MIP-1 beta)). The cellular signaling involved activation of c-Raf, extracellular signal-regulated kinase-1 (ERK-1)/ERK-2, and c-Jun N-terminal kinase, but not p38 mitogen-activated protein kinase. This is further supported by the data showing that A beta causes phosphorylation of ERK-1/ERK-2, which, in turn, activates Elk-1. Furthermore, A beta mediated a time-dependent increase in DNA binding activity of early growth response-1 (Egr-1) and AP-1, but not of NF-kappa B and CREB. Moreover, A beta-induced Egr-1 DNA binding activity was reduced >60% in THP-1 cells transfected with small interfering RNA duplexes for Egr-1 mRNA. We show that A beta-induced expression of TNF-alpha, IL-1 beta, MCP-1, IL-8, and MIP-1 beta was abrogated in Egr-1 small inhibitory RNA-transfected cells. Our results indicate that A beta-induced expression of cytokines (TNF-alpha and IL-1 beta) and chemokines (MCP-1, IL-8, and MIP-1 beta) in THP-1 monocytes involves activation of ERK-1/ERK-2 and downstream activation of Egr-1. The inhibition of Egr-1 by Egr-1 small inhibitory RNA may represent a potential therapeutic target to ameliorate the inflammation and progression of AD.

Distinct intragraft response pattern in relation to graft size in liver transplantation

BACKGROUND

The molecular mechanism of small-for-size graft injury remains unclear. The aim of this study is to investigate the gene expression pattern of acute phase response in relation to graft size in a rat-liver transplantation model.

METHODS

A rat orthotopic liver transplantation model using 30%, 50%, and whole grafts was used. The graft survival rates and liver morphology were compared among the three groups. Two transcription factors, nuclear factor (NF)-kappaB (p65) and early growth response (Egr-1), and their downstream genes were compared.

RESULTS

According to the graft size, the rats were grouped as follows: group 1 (n=20), 32% (24-47%); group 2 (n=10), 56% (50-65%); and group 3 (n=10), 104% (89-120%). The 7-day survival rates were 20% (P=0.039 vs. group 2, P=0.000 vs. group 3), 60%, and 100% in groups 1, 2, and 3, respectively. Dilation of hepatic sinusoids and vacuolization of hepatocytes were observed in group 1. Up-regulation of Egr-1 and endothelin (ET)-1 and over-expression of nitric oxide synthase (iNOS) was found in group 1, but heme oxygenase (HO)-1 and A20 were down-regulated. At 24 hours after reperfusion, the intragraft protein level of heat-shock protein (Hsp)-70 was significantly lower in group 1 than that in group 3 (12.4 vs. 17.0 ng/mL, P=0.04). More apoptotic nuclei were found in group 1.

CONCLUSIONS

Small-for-size graft injury was related to early over-expression of Egr-1 associated with up-regulation of ET-1 and deterioration of intracellular homeostasis reflected by down-regulation of Hsps and A20.