Hypoxia-associated induction of early growth response-1 gene expression

Different parts of the mussel Gigantidas haimaensis holobiont responded differently to deep-sea sampling stress

Acute environmental changes cause stress during conventional deep-sea biological sampling without in situ fixation and affect gene expressions of samples collected. However, the degree of influence and underlying mechanisms are hardly investigated. Here, we conducted comparative transcriptomic analyses between in situ and onboard fixed gills and between in situ and onboard fixed mantles of deep-sea mussel Gigantidas haimaensis to assess the effects of incidental sampling stress. Results showed that transcription, translation, and energy metabolism were upregulated in onboard fixed gills and mantles, thereby mobilizing rapid gene expression to tackle the stress. Autophagy and phagocytosis that related to symbiotic interactions between the host and endosymbiont were downregulated in the onboard fixed gills. These findings demonstrated that symbiotic gill and nonsymbiotic mantle responded differently to sampling stress, and symbiosis in the gill was perturbed. Further comparative metatranscriptomic analysis between in situ and onboard fixed gills revealed that stress response genes, peptidoglycan biosynthesis, and methane fixation were upregulated in the onboard fixed endosymbiotic Gammaproteobacteria inside the gills, implying that energy metabolism of the endosymbiont was increased to cope with sampling stress. Furthermore, comparative analysis between the mussel G. haimaensis and the limpet Bathyacmaea lactea transcriptomes resultedidentified six transcription factor orthologs upregulated in both onboard fixed mussel mantles and limpets, including sharply increased early growth response protein 1 and Kruppel-like factor 5. They potentially play key roles in initiating the response of sampled deep-sea macrobenthos to sampling stress. Our results clearly show that in situ fixed biological samples are vital for studying deep-sea environmental adaptation.

Dynamic changes in transcriptome during orthodontic tooth movement

OBJECTIVES

The objective of this study was to determine global changes in gene expression with next generation sequencing (NGS) in order to assess the biological effects of orthodontic tooth movement (OTM) on alveolar bone in a rat model.

MATERIALS AND METHODS

Thirty-five Wistar rats (age 14 weeks) were used in the study. The OTM was performed using closed coil Nickel-Titanium spring to apply a mesial force on maxillary first molars of 8-10 g. Three hours, 1, 3, 7 and 14 days after the placement of the appliance, rats were killed at each time point respectively. The alveolar bone, around left maxillary first molar, were excised on compression side. The samples were immediately frozen in liquid nitrogen for subsequent RNA extraction. Total RNA samples were prepared for mRNA sequencing using the Illumina kit. RNA-Seq reads were aligned to the rat genomes using the STAR Aligner and bioinformatic analysis was performed.

RESULTS

A total of 18 192 genes were determined. Day 1 has the highest number of differentially expressed genes (DEGs) observed with more upregulated than downregulated genes. A total of 2719 DEGs were identified to use as input for the algorithm. Six distinct clusters of temporal patterns were observed representing proteins that were differentially regulated indicating different expression kinetics. Principal component analysis (PCA) showed distinct clustering by time points and days 3, 7 and 14 share similar gene expression pattern.

CONCLUSIONS

Distinct gene expression pattern was observed at different time points studied. Hypoxia, inflammation and bone remodelling pathways are major mechanisms behind OTM.

Early Growth Response 1 Contributes to Renal IR Injury by Inducing Proximal Tubular Cell Apoptosis

Renal ischemia-reperfusion (IR) causes acute kidney injury due to oxidative stress, tubular inflammation, and apoptosis. Early growth response 1 (Egr-1) is a transcription factor belonging to the immediate early gene family and is known to regulate cell proliferation, differentiation, and survival. Egr-1 expression is induced during renal IR; however, its pathogenic role and underlying mechanisms remain elusive. Here, we investigated the function of Egr-1 during renal IR using C57BL/6 mice and cultured renal proximal tubular HK-2 cells. Egr-1 expression increased immediately, 1-4 h after IR, whereas plasma creatinine and oxidative stress increased progressively over 24 h after IR. Egr-1 overexpression showed greater increases in plasma creatinine, renal tubular injury, and apoptosis than in the control after IR. Egr-1 overexpression also showed significant neutrophil infiltration and increased pro-inflammatory cytokines (TNF-α, MIP-2, and IL-6) after IR. Consistently, proximal tubular HK-2 cells showed immediate induction of Egr-1 at 1 h after hypoxia and reoxygenation, where its downstream target, p53, was also increased. Interestingly, Egr-1 overexpression enhanced p53 levels and tubular apoptosis, while the knockdown of Egr-1 reduced p53 levels and tubular apoptosis after H2O2 treatment. Egr-1 was recruited to the p53 promoter, which activates p53 transcription, and Egr-1 induction occurred through Erk/JNK signaling kinases, as the specific inhibitors blocked its expression. Taken together, these results show that Egr-1 is upregulated in proximal tubular cells and contributes to renal IR injury by inducing tubular apoptosis, mediated by p53 transcriptional activation. Thus, Egr-1 could be a potential therapeutic target for renal IR injury.

Insight into the transcription factors regulating Ischemic Stroke and Glioma in Response to Shared Stimuli

Cerebral ischemic stroke and glioma are the two leading causes of patient mortality globally. Despite physiological variations, 1 in 10 people who have an ischemic stroke go on to develop brain cancer, most notably gliomas. In addition, glioma treatments have also been shown to increase the risk of ischemic strokes. Stroke occurs more frequently in cancer patients than in the general population, according to traditional literature. Unbelievably, these events share multiple pathways, but the precise mechanism underlying their co-occurrence remains unknown. Transcription factors (TFs), the main components of gene expression programmes, finally determine the fate of cells and homeostasis. Both ischemic stroke and glioma exhibit aberrant expression of a large number of TFs, which are strongly linked to the pathophysiology and progression of both diseases. The precise genomic binding locations of TFs and how TF binding ultimately relates to transcriptional regulation remain elusive despite a strong interest in understanding how TFs regulate gene expression in both stroke and glioma. As a result, the importance of continuing efforts to understand TF-mediated gene regulation is highlighted in this review, along with some of the primary shared events in stroke and glioma.

RAGE management: ETS1- EGR1 mediated transcriptional networks regulate angiogenic factors in wood frogs

Freeze-tolerant species, such as wood frogs (Rana sylvatica), are susceptible to multiple co-occurring stresses that they must overcome to survive. Freezing is accompanied by mechanical stress and dehydration due to ice crystal formation in the extracellular space, ischemia/anoxia due to interruption in blood flood, and hyperglycemia due to cryoprotective measures. Wood frogs can survive dehydration, anoxia, and high glucose stress independently of freezing, thereby creating a multifactorial model for studying freeze-tolerance. Oxidative stress and high glucose levels favors the production of pro-oxidant molecules and advanced glycation end product (AGE) adducts that could cause substantial cellular damage. In this study, the involvement of the high mobility group box 1 (HMGB1)-AGE/RAGE (receptor for AGE) axis and the regulation of ETS1 and EGR1-mediated angiogenic responses were investigated in liver of wood frogs expose to freeze/thaw, anoxia/reoxygenation and dehydration/rehydration treatments. HMGB1 and not AGE-adducts are likely to induce the activation of ETS1 and EGR1 via the RAGE pathway. The increase in nuclear localization of both ETS1 and EGR1, but not DNA binding activity in response to stress hints to a potential spatial and temporal regulation in inducing angiogenic factors. Freeze/thaw and dehydration/rehydration treatments increase the levels of both pro- and anti-angiogenic factors, perhaps to prepare for the distribution of cryoprotectants or enable the repair of damaged capillaries and wounds when needed. Overall, wood frogs appear to anticipate the need for angiogenesis in response to freezing and dehydration but not anoxic treatments, probably due to mechanical stress associated with the two former conditions.

Pathophysiology of deep vein thrombosis

Deep venous thrombosis is a frequent, multifactorial disease and a leading cause of morbidity and mortality. Most of the time deep venous thrombosis is triggered by the interaction between acquired risk factors, such as hip fracture, pregnancy, and immobility, and hereditary risk factors such as thrombophilias. The mechanisms underlying deep venous thrombosis are not fully elucidated; however, in recent years, important advances have shed light on the role of venous flow, endothelium, platelets, leukocytes, and the interaction between inflammation and hemostasis. It has been described that the alteration of venous blood flow produces endothelial activation, favoring the adhesion of platelets and leukocytes, which, through tissue factor expression and neutrophil extracellular traps formation, contribute to the activation of coagulation, trapping more cells, such as red blood cells. Thus, the concerted interaction of these phenomena allows the formation and growth of the thrombus. In this work, the main mechanisms involved in the pathophysiology of deep vein thrombosis will be described.

Pdx1 Is Transcriptionally Regulated by EGR-1 during Nitric Oxide-Induced Endoderm Differentiation of Mouse Embryonic Stem Cells

The transcription factor, early growth response-1 (EGR-1), is involved in the regulation of cell differentiation, proliferation, and apoptosis in response to different stimuli. EGR-1 is described to be involved in pancreatic endoderm differentiation, but the regulatory mechanisms controlling its action are not fully elucidated. Our previous investigation reported that exposure of mouse embryonic stem cells (mESCs) to the chemical nitric oxide (NO) donor diethylenetriamine nitric oxide adduct (DETA-NO) induces the expression of early differentiation genes such as pancreatic and duodenal homeobox 1 (Pdx1). We have also evidenced that Pdx1 expression is associated with the release of polycomb repressive complex 2 (PRC2) and P300 from the Pdx1 promoter; these events were accompanied by epigenetic changes to histones and site-specific changes in the DNA methylation. Here, we investigate the role of EGR-1 on Pdx1 regulation in mESCs. This study reveals that EGR-1 plays a negative role in Pdx1 expression and shows that the binding capacity of EGR-1 to the Pdx1 promoter depends on the methylation level of its DNA binding site and its acetylation state. These results suggest that targeting EGR-1 at early differentiation stages might be relevant for directing pluripotent cells into Pdx1-dependent cell lineages.

Matrix Metalloproteinases Shape the Tumor Microenvironment in Cancer Progression

Cancer progression with uncontrolled tumor growth, local invasion, and metastasis depends largely on the proteolytic activity of numerous matrix metalloproteinases (MMPs), which affect tissue integrity, immune cell recruitment, and tissue turnover by degrading extracellular matrix (ECM) components and by releasing matrikines, cell surface-bound cytokines, growth factors, or their receptors. Among the MMPs, MMP-14 is the driving force behind extracellular matrix and tissue destruction during cancer invasion and metastasis. MMP-14 also influences both intercellular as well as cell-matrix communication by regulating the activity of many plasma membrane-anchored and extracellular proteins. Cancer cells and other cells of the tumor stroma, embedded in a common extracellular matrix, interact with their matrix by means of various adhesive structures, of which particularly invadopodia are capable to remodel the matrix through spatially and temporally finely tuned proteolysis. As a deeper understanding of the underlying functional mechanisms is beneficial for the development of new prognostic and predictive markers and for targeted therapies, this review examined the current knowledge of the interplay of the various MMPs in the cancer context on the protein, subcellular, and cellular level with a focus on MMP14.

Molecular Characterization of NDL1-AGB1 Mediated Salt Stress Signaling: Further Exploration of the Role of NDL1 Interacting Partners

Salt stress is considered to be the most severe abiotic stress. High soil salinity leads to osmotic and ionic toxicity, resulting in reduced plant growth and crop production. The role of G-proteins during salt stresses is well established. AGB1, a G-protein subunit, not only plays an important role during regulation of Na⁺ fluxes in roots, but is also involved in the translocation of Na⁺ from roots to shoots. N-Myc Downregulated like 1 (NDL1) is an interacting partner of G protein βγ subunits and C-4 domain of RGS1 in Arabidopsis. Our recent in-planta expression analysis of NDL1 reported changes in patterns during salt stress. Based on these expression profiles, we have carried out functional characterization of the AGB1-NDL1 module during salinity stress. Using various available mutant and overexpression lines of NDL1 and AGB1, we found that NDL1 acts as a negative regulator during salt stress response at the seedling stage, an opposite response to that of AGB1. On the other hand, during the germination phase of the plant, this role is reversed, indicating developmental and tissue specific regulation. To elucidate the mechanism of the AGB1-NDL1 module, we investigated the possible role of the three NDL1 stress specific interactors, namely ANNAT1, SLT1, and IDH-V, using yeast as a model. The present study revealed that NDL1 acts as a modulator of salt stress response, wherein it can have both positive as well as negative functions during salinity stress. Our findings suggest that the NDL1 mediated stress response depends on its developmental stage-specific expression patterns as well as the differential presence and interaction of the stress-specific interactors.

Systematical Identification of the Protective Effect of Danhong Injection and BuChang NaoXinTong Capsules on Transcription Factors in Cerebral Ischemia Mice Brain

Cerebral ischemia has led to a high rate of both disability and mortality with massive healthcare costs. Although transcriptional regulation is typically mediated by different combinations of TFs, a combined regulatory unit to synergistically activate transcription has remained unclear in cerebral ischemia, especially in different drug treatments. In this study, TFs alterations after 6 h cerebral ischemic injury and repair were performed by a concatenated tandem array of consensus transcription factor response elements (catTFREs), and vital TFs were obtained by TFs-target imbalanced network. Drug intervention used Danhong injection (DHI) and BNC (BuChang NaoXinTong Capsules), which has been widely prescribed in Chinese herb medicine for the treatment of cerebrovascular and cardiovascular diseases. There were 198 TFs identified after 6 h MCAO operation, and six TFs (Sox2, Smad3, FoxO1, Creb1, Egr,1 and Smad4) were considered as critical TFs in response to cerebral ischemia. Moreover, Smad3 was identified as a hub TF among six vital TFs, and the transcription activity of Smad3 was further verified. These 6 TFs were all reversed by DHI or BNC, indicating different medications may regulate different transcription factors through TF synergy. Moreover, validation results indicated that Smad3 was a putative target TF for DHI and BNC-mediated protection against cerebral ischemia. The observations of the present study provide a fresh understanding of biomolecules and possible new avenues for therapeutic interventions, in addition to the new intervention pattern for different treatments for ischemia stroke.

RAGE against the stress: Mitochondrial suppression in hypometabolic hearts

The wood frog (Rana sylvatica) can tolerate full body freezing in winter. As a protective response, wood frogs dehydrate their cells and accumulate large quantities of glucose as an intracellular cryoprotectant. Freezing causes ischemia since blood delivery to organs is interrupted. Fascinatingly, wood frogs can tolerate dehydration, extreme hyperglycemia, and anoxia independently of freezing. In response to low oxygen levels, wood frogs strategically reduce their metabolic rates and allocate the finite amount of intracellular fuel available to pro-survival processes while reducing or interrupting all others. In this study, the involvement of advanced glycation end products (AGEs) and the high mobility group box 1 (HMGB1) protein in activating RAGE (AGE receptor) were investigated. The results show that freezing, anoxia and dehydration induced the expression of total HMGB1 and its acetylation in the heart. RAGE levels were induced in response to all stress conditions, which resulted in differential regulation of the ETS1 transcription factor. While the nuclear localization of total ETS1 was not affected, the DNA binding activity of total and its active form increased in response to freezing and dehydration but not in response to anoxia. Current results indicate that ETS1 acts as a transcriptional activator for peroxiredoxin 1 in response to freezing but acts as a transcriptional repressor of several nuclear-encoded mitochondrial genes in response to all stresses. Altogether, current results show that the HMGB1/RAGE axis may activate ETS1 and that this activation could result in both transcriptional activation and/or repression in a stress-dependent manner.

The Importance of the Tumor Microenvironment and Hypoxia in Delivering a Precision Medicine Approach to Veterinary Oncology

Treating individual patients on the basis of specific factors, such as biomarkers, molecular signatures, phenotypes, environment, and lifestyle is what differentiates the precision medicine initiative from standard treatment regimens. Although precision medicine can be applied to almost any branch of medicine, it is perhaps most easily applied to the field of oncology. Cancer is a heterogeneous disease, meaning that even though patients may be histologically diagnosed with the same cancer type, their tumors may have different molecular characteristics, genetic mutations or tumor microenvironments that can influence prognosis or treatment response. In this review, we describe what methods are currently available to clinicians that allow them to monitor key tumor microenvironmental parameters in a way that could be used to achieve precision medicine for cancer patients. We further describe exciting novel research involving the use of implantable medical devices for precision medicine, including those developed for mapping tumor microenvironment parameters (e.g., O2, pH, and cancer biomarkers), delivering local drug treatments, assessing treatment responses, and monitoring for recurrence and metastasis. Although these research studies have predominantly focused on and were tailored to humans, the results and concepts are equally applicable to veterinary patients. While veterinary clinical studies that have adopted a precision medicine approach are still in their infancy, there have been some exciting success stories. These have included the development of a receptor tyrosine kinase inhibitor for canine mast cell tumors and the production of a PCR assay to monitor the chemotherapeutic response of canine high-grade B-cell lymphomas. Although precision medicine is an exciting area of research, it currently has failed to gain significant translation into human and veterinary healthcare practices. In order to begin to address this issue, there is increasing awareness that cross-disciplinary approaches involving human and veterinary clinicians, engineers and chemists may be needed to help advance precision medicine toward its full integration into human and veterinary clinical practices.

Expression and prognostic value of the transcription factors EGR1 and EGR3 in gliomas

Most glioblastoma patients have a dismal prognosis, although some survive several years. However, only few biomarkers are available to predict the disease course. EGR1 and EGR3 have been linked to glioblastoma stemness and tumour progression, and this study aimed to investigate their spatial expression and prognostic value in gliomas. Overall 207 gliomas including 190 glioblastomas were EGR1/EGR3 immunostained and quantified. A cohort of 21 glioblastomas with high P53 expression and available tissue from core and periphery was stained with double-immunofluorescence (P53-EGR1 and P53-EGR3) and quantified.EGR1 expression increased with WHO-grade, and declined by 18.9% in the tumour periphery vs. core (P = 0.01), while EGR3 expression increased by 13.8% in the periphery vs. core (P = 0.04). In patients with high EGR1 expression, 83% had methylated MGMT-promoters, while all patients with low EGR1 expression had un-methylated MGMT-promoters. High EGR3 expression in MGMT-methylated patients was associated with poor survival (HR = 1.98; 95%CI 1.22–3.22; P = 0.006), while EGR1 high/EGR3 high, was associated with poor survival vs. EGR1 high/EGR3 low (HR = 2.11; 95%CI 1.25–3.56; P = 0.005). EGR1 did not show prognostic value, but could be involved in MGMT-methylation. Importantly, EGR3 may be implicated in cell migration, while its expression levels seem to be prognostic in MGMT-methylated patients.

Forty Years of Basic and Translational Heparanase Research

This review summarizes key developments in the heparanase field obtained 20 years prior to cloning of the HPSE gene and nearly 20 years after its cloning. Of the numerous publications and review articles focusing on heparanase, we have selected those that best reflect the progression in the field as well as those we regard important accomplishments with preference to studies performed by scientists and groups that contributed to this book. Apart from a general 'introduction' and 'concluding remarks', the abstracts of these studies are presented essentially as published along the years. We apologize for not being objective and not being able to include some of the most relevant abstracts and references, due to space limitation. Heparanase research can be divided into two eras. The first, initiated around 1975, dealt with identifying the enzyme, establishing the relevant assay systems and investigating its biological activities and significance in cancer and other pathologies. Studies performed during the first area are briefly introduced in a layman style followed by the relevant abstracts presented chronologically, essentially as appears in PubMed. The second era started in 1999 when the heparanase gene was independently cloned by 4 research groups [1-4]. As expected, cloning of the heparanase gene boosted heparanase research by virtue of the readily available recombinant enzyme, molecular probes, and anti-heparanase antibodies. Studies performed during the second area are briefly introduced followed by selected abstracts of key findings, arranged according to specific topics.

Effects of Hyperoxia on the Refraction in Murine Neonatal and Adult Models

Whether hyperoxia affects the refraction in neonatal and adult mice is unknown. The mice exposed to 85% oxygen at postnatal 8 days (P8d) for 3 days and the mice exposed to normal air were assigned to the neonatal hyperoxia and normoxia groups, respectively. The refraction, the corneal curvature radius (CR) and the axial length (AL) were measured at P30d and P47d. Postnatal 6 weeks (P6w) adult mice were divided into the adult hyperoxia and normoxia groups. These parameters were measured before oxygen exposure, after 1 and 6 weeks, and every 7 weeks. The lens elasticity was measured at P7w and P26w by enucleation. The neonatal hyperoxia group showed a significantly larger myopic change than the neonatal normoxia group (P47d −6.56 ± 5.89 D, +4.11 ± 2.02 D, p < 0.001), whereas the changes in AL were not significantly different (P47d, 3.31 ± 0.04 mm, 3.31 ± 0.05 mm, p = 0.852). The adult hyperoxia group also showed a significantly larger myopic change (P12w, −7.20 ± 4.09 D, +7.52 ± 2.54 D, p < 0.001). The AL did not show significant difference (P12w, 3.44 ± 0.03 mm, 3.43 ± 0.01 mm, p = 0.545); however, the CR in the adult hyperoxia group was significantly smaller than the adult normoxia group (P12w, 1.44 ± 0.03 mm, 1.50 ± 0.03 mm, p = 0.003). In conclusion, hyperoxia was demonstrated to induce myopic shift both in neonatal and adult mice, which was attributed to the change in the CR rather than the AL. Elucidation of the mechanisms of hyperoxia and the application of this result to humans should be carried out in future studies.

Arabidopsis NDL-AGB1 modules Play Role in Abiotic Stress and Hormonal Responses Along with Their Specific Functions

Arabidopsis N-MYC Downregulated Like Proteins (NDLs) are interacting partners of G-Protein core components. Animal homologs of the gene family N-myc downstream regulated gene (NDRG) has been found to be induced during hypoxia, DNA damage, in presence of reducing agent, increased intracellular calcium level and in response to metal ions like nickel and cobalt, which indicates the involvement of the gene family during stress responses. ArabidopsisNDL gene family contains three homologs NDL1, NDL2 and NDL3 which share up to 75% identity at protein level. Previous studies on NDL proteins involved detailed characterization of the role of NDL1; roles of other two members were also established in root and shoot development using miRNA knockdown approach. Role of entire family in development has been established but specific functions of NDL2 and NDL3 if any are still unknown. Our in-silico analysis of NDLs promoters reveled that all three members share some common and some specific transcription factors (TFs) binding sites, hinting towards their common as well as specific functions. Based on promoter elements characteristics, present study was designed to carry out comparative analysis of the Arabidopsis NDL family during different stages of plant development, under various abiotic stresses and plant hormonal responses, in order to find out their specific and combined roles in plant growth and development. Developmental analysis using GUS fusion revealed specific localization/expression during different stages of development for all three family members. Stress analysis after treatment with various hormonal and abiotic stresses showed stress and tissue-specific differential expression patterns for all three NDL members. All three NDL members were collectively showed role in dehydration stress along with specific responses to various treatments. Their specific expression patterns were affected by presence of interacting partner the Arabidopsis heterotrimeric G-protein β subunit 1 (AGB1). The present study will improve our understanding of the possible molecular mechanisms of action of the independent NDL–AGB1 modules during stress and hormonal responses. These findings also suggest potential use of this knowledge for crop improvement.

HIF-1 regulation of miR-29c impairs SERCA2 expression and cardiac contractility

The principal regulator of cellular response to low oxygen is hypoxia-inducible factor (HIF)-1, which is stabilized in several forms of heart failure. Our laboratory developed a mouse strain in which a stable form of HIF-1 can be inducibly expressed in cardiomyocytes. Strikingly, these mice show a rapid decrease in cardiac contractility and a rapid loss of SERCA2 protein, which is also seen in heart failure. Interestingly, while the SERCA2 transcript decreased, it did not fully account for the observed decrease in protein. We therefore investigated whether HIF-1-regulated microRNA could impair SERCA translation. Multiple screening analyses identified the microRNA miR-29c to be substantially upregulated upon HIF-1 induction and to have complementarity to SERCA, and therefore be a potential regulator of SERCA2 expression in hypoxia. Subsequent evaluation confirmed that miR-29c reduced SERCA2 expression and Ca²⁺ reuptake. Additionally, administration of an antagonist sequence (antimir) improved cardiac contractility and SERCA2 expression in HIF transgenic mice. To extend the significance of these findings, we examined miR-29c expression in physiological hypoxia. Surprisingly, miR-29c decreased in these settings. We also treated mice with antimir before infarction to see if further suppression of miR-29c could improve cardiac function. While no improvement in contractility or SERCA2 was observed, reduction of heart size after infarction indicated that the antimir could modulate cardiac physiology. These results demonstrate that while a HIF-1-regulated microRNA, miR-29c, can reduce SERCA2 expression and contractility, additional factors in the ischemic milieu may limit these effects. Efforts to develop miRNA-based therapies will need to explore and account for these additional countervailing effects. NEW & NOTEWORTHY Our study demonstrated hypoxia-inducible factor-1-dependent upregulation of miR-29c, which, in turn, inhibited SERCA2 expression and reduced cardiac contractility in a transgenic overexpression system. Interestingly, these results were not recapitulated in a murine myocardial infarction model. These results underscore the complexity of the pathological environment and highlight the need for therapeutic target validation in physiologically relevant models.

Hyperglycemia induced early growth response-1 regulates vascular dysfunction in human retinal endothelial cells

Early growth response-1 (Egr-1) protein upregulation is reported in diabetes and vascular disorders. This study aims at deciphering its role in hyperglycemia induced changes of retinal endothelium. Human retinal endothelial cells (hRECs) were exposed to hyperglycemia (25mM) and normoglycemia (5.5mM). Gene silencing was done using siRNA against Egr-1. Transcript and protein level analysis of Egr-1 and gene targets were done using qPCR and immunoblotting respectively in hRECs, diabetic and nondiabetic human retina and immunofluorescence for localization in retinal sections. Hyperglycemia induced Egr-1 and vascular endothelial growth factor-A (VEGF-A) but not pigment epithelium derived factor (PEDF) in hRECs. Expression of Egr-1 repressor NGFI-A binding protein-2 (NAB-2) was unaltered. Egr-1 downstream gene targets, tissue factor (TF) and intercellular adhesion molecule-1 (ICAM-1) expression were increased in hRECs which was reduced by Egr-1 silencing in hyperglycemia. Diabetic retina, showed an increase in Egr-1, VEGF-A and gene target TF, ICAM-1 but not NAB-2 and PEDF similar to the changes seen in hyperglycemic hRECs. Hyperglycemic induction of Egr-1 and absence of NAB-2 repression in retinal endothelium, up-regulates downstream genes involved in pro-thrombotic and pro-inflammatory pathways linking Egr-1 in diabetes mediated vascular aberration of retina.

Estrogen induces EGR1 to fine-tune its actions on uterine epithelium by controlling PR signaling for successful embryo implantation

The harmonized actions of ovarian E₂ and progesterone (P₄) regulate the proliferation and differentiation of uterine cells in a spatiotemporal manner. Imbalances between these hormones often lead to infertility and gynecologic diseases. Whereas numerous factors that are involved in P₄ signaling have been identified, few local factors that mediate E₂ actions in the uterus have been revealed. Here, we demonstrate that estrogen induces the transcription factor, early growth response 1 ( Egr1), to fine-tune its actions in uterine epithelial cells (ECs) that are responsible for uterine receptivity for embryo implantation. In the presence of exogenous gonadotrophins, ovulation, fertilization, and embryonic development normally occur in Egr1^-/- mice, but these animals experience the complete failure of embryo implantation with reduced artificial decidualization. Although serum levels of E₂ and P₄ were comparable between Egr1^+/+ and Egr1^-/- mice on d 4 of pregnancy, aberrantly reduced levels of progesterone receptor in Egr1^-/- uterine ECs caused enhanced E₂ activity and impaired P₄ response. Ultrastructural analyses revealed that Egr1^-/- ECs are not fully able to provide proper uterine receptivity. Uterine mRNA landscapes in Egr1^-/- mice revealed that EGR1 controls the expression of a subset of E₂-regulated genes. In addition, P₄ signaling was unable to modulate estrogen actions, including those that are involved in cell-cycle progression, in ECs that were deficient in EGR1. Furthermore, primary coculture of Egr1^-/- ECs with Egr1^+/+ stromal cells, and vice versa, supported the notion that Egr1 is required to modulate E₂ actions on ECs to prepare the uterine environment for embryo implantation. In contrast to its role in ECs, loss of Egr1 in stroma significantly reduced stromal cell proliferation. Collectively, our results demonstrate that E₂ induces EGR1 to streamline its actions for the preparation of uterine receptivity for embryo implantation in mice.-Kim, H.-R., Kim, Y. S., Yoon, J. A., Yang, S. C., Park, M., Seol, D.-W., Lyu, S. W., Jun, J. H., Lim, H. J., Lee, D. R., Song, H. Estrogen induces EGR1 to fine-tune its actions on uterine epithelium by controlling PR signaling for successful embryo implantation.

GPER-independent inhibition of adrenocortical cancer growth by G-1 involves ROS/Egr-1/BAX pathway

We previously demonstrated that treatment of the H295R adrenocortical cancer cell line with the non-steroidal, high-affinity GPER (G protein-coupled estrogen receptor 1) agonist G-1 reduced tumor growth in vitro and in vivo through a GPER independent action. Moreover, we observed that G-1 treatment induces cell-cycle arrest and apoptosis following a sustained ERK1/2 activation. However, the precise mechanisms causing these effects were not clarified. Starting from our preliminary published results, we performed a microarray study that clearly evidenced a strong and significative up-regulation of EGR-1 gene in H295R cells treated for 24h with micromolar concentration of G-1. The microarray findings were confirmed by RT-PCR and Western-blot analysis as well as by immunofluorescence that revealed a strong nuclear staining for EGR-1 after G-1 treatment. EGR-1 is a point of convergence of many intracellular signaling cascades that control tumor cell growth and proliferation as well as others that relate to cell death machinery. Here we found that the increased Egr-1 expression was a consequence of G-1-mediated ROS-dependent ERK activation that were promptly reversed by the presence of the antioxidant n-acetyl-cysteine. Finally, we observed that silencing EGR-1 gene expression reversed the main effects induced by G-1 in ACC cells, including upregulation of the negative regulator of cell cycle, p21^Waf1/Cip1 and the positive regulator of mitochondrial apoptotic pathway, BAX, as well as the cell growth inhibition. The identified ROS/MAPK/Egr-1/BAX pathway as a potential off-target effect of the G-1 could be useful in implementing the pharmacological approach for ACC therapy.

Cellular Prion Protein (PrPc) and Hypoxia: True to Each Other in Good Times and in Bad, in Sickness, and in Health

The cellular prion protein (PrP^c) and hypoxia appear to be tightly intertwined. Beneficial effects of PrP^c on neuronal survival under hypoxic conditions such as focal cerebral ischemia are strongly supported. Conversely, increasing evidence indicates detrimental effects of increased PrP^c expression on cancer progression, another condition accompanied by low oxygen tensions. A switch between anaerobic and aerobic metabolism characterizes both conditions. A cellular process that might unite both is glycolysis. Putative role of PrP^c in stimulation of glycolysis in times of need is indeed thought provoking. A significance of astrocytic PrP^c expression for neuronal survival under hypoxic conditions and possible association of PrP^c with the astrocyte-neuron lactate shuttle is considered. We posit PrP^c-induced lactate production via transactivation of lactate dehydrogenase A by hypoxia inducible factor 1α as an important factor for survival of both neurons and tumor cells in hypoxic microenvironment. Concomitantly, we discuss a cross-talk between Wnt/β-catenin and PI3K/Akt signaling pathways in executing PrP^c-induced activation of glycolysis. Finally, we would like to emphasize that we see a great potential in joining expertise from both fields, neuroscience and cancer research in revealing the mechanisms underlying hypoxia-related pathologies. PrP^c may prove focal point for future research.

Src tyrosine kinase mediates endothelin-1-induced early growth response protein-1 expression via MAP kinase-dependent pathways in vascular smooth muscle cells

We have previously demonstrated that the non-receptor protein tyrosine kinase (NR-PTK) c-Src is an upstream regulator of endothelin-1 (ET-1) and angiotensin II-induced activation of protein kinase B (PKB) signaling in vascular smooth muscle cells (VSMCs). We have also demonstrated that ET-1 potently induces the expression of the early growth response protein-1 (Egr-1), a zinc finger transcription factor that is overexpressed in models of vascular diseases, such as atherosclerosis. However, the involvement of c-Src in ET-1‑induced Egr-1 expression has not yet been investigated and its role in mitogen-activated protein kinase (MAPK) signaling remains controversial. Therefore, the aim of the present study was to examine the role of c-Src in the ET-1-induced phosphorylation of extracellular signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK) and p38 MAPK, 3 key members of the MAPK family and in the regulation of Egr-1 expression in rat aortic A10 VSMCs. ET-1 rapidly induced the phosphorylation of MAPKs, as well as the expression of Egr-1; however, treatment of the VSMCs with PP2, a specific pharmacological inhibitor of c-Src, dose-dependently reduced the phosphorylation of the 3 MAPKs and the expression of Egr-1 induced by ET-1. Furthermore, in mouse embryonic fibroblasts (MEFs) deficient in c-Src (SYF), the ET-1-induced Egr-1 expression and MAPK phosphorylation were significantly suppressed, as compared to MEFs expressing normal Src levels. These results suggest that c-Src plays a critical role in mediating ET-1-induced MAPK phosphorylation and Egr-1 expression in VSMCs.

Functional and molecular factors associated with TAPSE in hypoxic pulmonary hypertension

Adaptation of the right ventricle (RV) to increased afterload is crucial for survival in pulmonary hypertension (PH), but it is challenging to assess RV function and identify associated molecular mechanisms. The aim of the current study was to analyze the relationship between invasive and noninvasive parameters of RV morphology and function and associated molecular changes. The response of mice to normobaric hypoxia was assessed by hechocardiography, invasive hemodynamics, and histological and molecular analyses. Plasma levels of possibly novel markers of RV remodeling were measured by ELISA in patients with idiopathic pulmonary arterial hypertension (IPAH) and matched healthy controls. Chronic hypoxia-induced PH was accompanied by significantly decreased tricuspid annular plane systolic excursion (TAPSE) and unchanged RV contractility index and tau. RV hypertrophy was present without an increase in fibrosis. There was no change in α- and β-major histocompatibility class or natriuretic peptides expression. Comparative microarray analysis identified two soluble factors, fibroblast growth factor-5 (FGF5) and interleukin-22 receptor alpha-2 (IL22RA2), as being possibly associated with RV remodeling. We observed significantly higher plasma levels of IL22RA2, but not FGF5, in patients with IPAH. Hypoxic pulmonary hypertension in a stage of RV remodeling with preserved systolic function is associated with decreased pulmonary vascular compliance, mild diastolic RV dysfunction, and significant decrease in TAPSE. Subtle gene expression changes in the RV vs. the left ventricle upon chronic hypoxia suggest that the majority of changes are due to hypoxia and not due to changes in afterload. Increased IL22RA2 levels might represent a novel RV adaptive mechanism.

Increased Expression of EGR-1 in Diabetic Human Adipose Tissue-Derived Mesenchymal Stem Cells Reduces Their Wound Healing Capacity

The prevalence of type 2 diabetes mellitus (T2DM), which leads to diabetic complications, has been increasing worldwide. The possible applications of T2DM-derived stem cells in cell therapy are limited because their characteristics are still not fully understood. In this study, we characterized adipose tissue-derived mesenchymal stem cells (AT-MSCs) from diabetic patients (dAT-MSCs) and found that insulin receptor substrate-1 (IRS-1) was highly phosphorylated at serine 636/639 in dAT-MSCs. Moreover, we found that early growth response factor-1 (EGR-1) and its target genes of PTEN and GGPS1 were highly expressed in dAT-MSCs in comparison to healthy donor-derived AT-MSCs (nAT-MSCs). We observed impaired wound healing after the injection of dAT-MSCs in the ischemic flap mouse model. The expressions of EGR-1 and its target genes were diminished by small hairpin RNA-targeted EGR-1 (shEGR-1) and treatment with a mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) inhibitor (PD98059). Importantly, dAT-MSCs with shEGR-1 were able to restore the wound healing ability in the mouse model. Interestingly, under hypoxic conditions, hypoxia-inducible factor-1α (HIF-1α) can bind to the EGR-1 promoter in dAT-MSCs, but not in nAT-MSCs. Together, these results demonstrate that the expression of EGR-1 was upregulated in dAT-MSCs through two pathways: the main regulatory pathway is the MAPK/ERK pathway, the other is mediated by HIF-1α through direct transcriptional activation at the promoter region of the EGR1 gene. Our study suggests that dAT-MSCs may contribute to microvascular damage and delay wound healing through the overexpression of EGR-1. Interrupting the expression of EGR-1 in dAT-MSCs may be a useful treatment for chronic wounds in diabetic patients.

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.

Diverse Mechanisms of Sp1-Dependent Transcriptional Regulation Potentially Involved in the Adaptive Response of Cancer Cells to Oxygen-Deficient Conditions

The inside of a tumor often contains a hypoxic area caused by a limited supply of molecular oxygen due to aberrant vasculature. Hypoxia-inducible factors (HIFs) are major transcription factors that are required for cancer cells to adapt to such stress conditions. HIFs, complexed with the aryl hydrocarbon receptor nuclear translocator, bind to and activate target genes as enhancers of transcription. In addition to this common mechanism, the induction of the unfolded protein response and mTOR signaling in response to endoplasmic reticulum stress is also known to be involved in the adaptation to hypoxia conditions. Sp1 is a ubiquitously-expressed transcription factor that plays a vital role in the regulation of numerous genes required for normal cell function. In addition to the well-characterized stress response mechanisms described above, increasing experimental evidence suggests that Sp1 and HIFs collaborate to drive gene expression in cancer cells in response to hypoxia, thereby regulating additional adaptive responses to cellular oxygen deficiency. However, these characteristics of Sp1 and their biological merits have not been summarized. In this review, we will discuss the diverse mechanisms of transcriptional regulation by Sp1 and their potential involvement in the adaptive response of cancer cells to hypoxic tumor microenvironments.

Transcriptomic changes triggered by hypoxia: evidence for HIF-1α-independent, [Na+]i/[K+]i-mediated, excitation-transcription coupling

This study examines the relative impact of canonical hypoxia-inducible factor-1alpha- (HIF-1α and Na⁺_i/K⁺_i-mediated signaling on transcriptomic changes evoked by hypoxia and glucose deprivation. Incubation of RASMC in ischemic conditions resulted in ∼3-fold elevation of [Na⁺]_i and 2-fold reduction of [K⁺]_i. Using global gene expression profiling we found that Na⁺,K⁺-ATPase inhibition by ouabain or K⁺-free medium in rat aortic vascular smooth muscle cells (RASMC) led to the differential expression of dozens of genes whose altered expression was previously detected in cells subjected to hypoxia and ischemia/reperfusion. For further investigations, we selected Cyp1a1, Fos, Atf3, Klf10, Ptgs2, Nr4a1, Per2 and Hes1, i.e. genes possessing the highest increments of expression under sustained Na⁺,K⁺-ATPase inhibition and whose implication in the pathogenesis of hypoxia was proved in previous studies. In ouabain-treated RASMC, low-Na⁺, high-K⁺ medium abolished amplification of the [Na⁺]_i/[K⁺]_i ratio as well as the increased expression of all tested genes. In cells subjected to hypoxia and glucose deprivation, dissipation of the transmembrane gradient of Na⁺ and K⁺ completely eliminated increment of Fos, Atf3, Ptgs2 and Per2 mRNAs and sharply diminished augmentation expression of Klf10, Edn1, Nr4a1 and Hes1. In contrast to low-Na⁺, high-K⁺ medium, RASMC transfection with Hif-1a siRNA attenuated increments of Vegfa, Edn1, Klf10 and Nr4a1 mRNAs triggered by hypoxia but did not impact Fos, Atf3, Ptgs2 and Per2 expression. Thus, our investigation demonstrates, for the first time, that Na⁺_i/K⁺_i-mediated, Hif-1α- -independent excitation-transcription coupling contributes to transcriptomic changes evoked in RASMC by hypoxia and glucose deprivation.

Hypoxia-mediated downregulation of miRNA biogenesis promotes tumour progression

Cancer-related deregulation of miRNA biogenesis has been suggested, but the underlying mechanisms remain elusive. Here we report a previously unrecognized effect of hypoxia in the downregulation of Drosha and Dicer in cancer cells that leads to dysregulation of miRNA biogenesis and increased tumour progression. We show that hypoxia-mediated downregulation of Drosha is dependent on ETS1/ELK1 transcription factors. Moreover, mature miRNA array and deep sequencing studies reveal altered miRNA maturation in cells under hypoxic conditions. At a functional level, this phenomenon results in increased cancer progression in vitro and in vivo, and data from patient samples are suggestive of miRNA biogenesis downregulation in hypoxic tumours. Rescue of Drosha by siRNAs targeting ETS1/ELK1 in vivo results in significant tumour regression. These findings provide a new link in the mechanistic understanding of global miRNA downregulation in the tumour microenvironment.

Egr1 is rapidly and transiently induced by estrogen and bisphenol A via activation of nuclear estrogen receptor-dependent ERK1/2 pathway in the uterus

Coordinate actions of ovarian estrogen (E2) and progesterone (P4) via their own receptors are critical for establishing uterine receptivity for embryo implantation in the uterus. E2 regulates expression of an array of genes to mediate its major actions on heterogeneous uterine cell types. Here we have investigated regulatory mechanism(s) of E2 and bisphenol A (BPA), an endocrine disruptor with potent estrogenic activity on expression of early growth response 1 (Egr1), a zinc finger transcription factor that regulates cell growth, differentiation and apoptosis in the uterus. Egr1 was rapidly and transiently induced by E2 and BPA mainly in stromal cells via nuclear estrogen receptor (ER)-ERK1/2 pathway. ICI 182,780, an ER antagonist, effectively inhibited their actions on EGR1 expression following ERK1/2 phosphorylation. Administration of pharmacological inhibitors for ERK1/2, but not AKT significantly blocked EGR1 expression induced by E2 and BPA. P4 effectively dampened action(s) of E2 and BPA on Egr1 expression via nuclear progesterone receptor. Its antagonistic effects were partially interfered with RU486 pretreatment. Interestingly, EGR1 is specifically induced in stromal cells surrounding implanting blastocyst. Collectively, our results show that through nuclear ER-dependent ERK1/2 phosphorylation, not only E2 but also endocrine disruptors with estrogenic activity such as BPA rapidly and transiently induce Egr1 which may be important for embryo implantation and decidualization in mouse uterus.

Effect of acute exacerbations on circulating endothelial, clotting and fibrinolytic markers in COPD patients

Patients with chronic obstructive pulmonary disease (COPD) are prone to clinical exacerbations that are associated with increased airway inflammation, a potent pro-thrombotic stimulus. Limited information is available on the mechanisms underlying the putative alterations of the endothelial-coagulative system during acute exacerbations. The aim was to investigate whether the activation of the endothelial-coagulative system occurs in association with the acute inflammatory response of COPD exacerbation. We monitored the blood levels of surrogate markers of inflammation: interleukin-6 (IL-6); endothelium damage: von Willebrand's factor (vWF); clotting activation: D-dimer (D-D), and prothrombin fragment 1+2 (F1+2); fibrinolytic response: plasminogen activator inhibitor 1 (PAI-1), in COPD subjects, during hospital admission and after clinical resolution. In 30 COPD subjects, IL-6, vWF, D-D and F1+2 levels were elevated during exacerbation and decreased significantly at clinical stability (IL-6, p = 0.005; vWF, p < 0.001; D-D, p < 0.001; F1+2, p < 0.001). PAI-1 levels did not change at exacerbation compared to clinically stable situations. Positive correlations were observed between several of the markers measured. Elevation of IL-6, vWF, D-D and F1+2 levels during COPD exacerbations implies a strict association between acute inflammation, endothelial activation and clotting initiation. This was not associated with a change in PAI-1, implying an increase in the fibrinolytic response to inflammation. The pro-thrombotic nature of COPD exacerbations sustained by enhanced clotting activation appears to be mitigated by excessive fibrinolysis.

The role of angiogenic factors in fibroid pathogenesis: potential implications for future therapy

BACKGROUND

It is well established that tumors are dependent on angiogenesis for their growth and survival. Although uterine fibroids are known to be benign tumors with reduced vascularization, recent work demonstrates that the vasculature of fibroids is grossly and microscopically abnormal. Accumulating evidence suggests that angiogenic growth factor dysregulation may be implicated in these vascular and other features of fibroid pathophysiology.

METHODS

Literature searches were performed in PubMed and Google Scholar for articles with content related to angiogenic growth factors and myometrium/leiomyoma. The findings are hereby reviewed and discussed.

RESULTS

Multiple growth factors involved in angiogenesis are differentially expressed in leiomyoma compared with myometrium. These include epidermal growth factor (EGF), heparin-binding-EGF, vascular endothelial growth factor, basic fibroblast growth factor, platelet-derived growth factor, transforming growth factor-β and adrenomedullin. An important paradox is that although leiomyoma tissues are hypoxic, leiomyoma feature down-regulation of key molecular regulators of the hypoxia response. Furthermore, the hypoxic milieu of leiomyoma may contribute to fibroid development and growth. Notably, common treatments for fibroids such as GnRH agonists and uterine artery embolization (UAE) are shown to work at least partly via anti-angiogenic mechanisms.

CONCLUSIONS

Angiogenic growth factors play an important role in mechanisms of fibroid pathophysiology, including abnormal vasculature and fibroid growth and survival. Moreover, the fibroid's abnormal vasculature together with its aberrant hypoxic and angiogenic response may make it especially vulnerable to disruption of its vascular supply, a feature which could be exploited for treatment. Further experimental studies are required in order to gain a better understanding of the growth factors that are involved in normal and pathological myometrial angiogenesis, and to assess the potential of anti-angiogenic treatment strategies for uterine fibroids.

Bench to bedside: new developments in our understanding of the pathophysiology of thrombosis

There has been a resurgent interest in the molecular and cellular mechanisms of thrombogenesis in venous thromboembolism (VTE). Improved animal models of VTE, combined with high-resolution microscopy techniques, have helped to uncover novel roles for blood cells including platelets and innate immune cells, particularly neutrophils. These insights are likely to result in novel disease biomarkers and perhaps even adjunctive anti-thrombotic therapies.

Enhanceosomes as integrators of hypoxia inducible factor (HIF) and other transcription factors in the hypoxic transcriptional response

Hypoxia is a prevalent attribute of the solid tumor microenvironment that promotes the expression of genes through posttranslational modifications and stabilization of alpha subunits (HIF1α and HIF2α) of hypoxia-inducible factors (HIFs). Despite significant similarities, HIF1 (HIF1α/ARNT) and HIF2 (HIF2α/ARNT) activate common as well as unique target genes and exhibit different functions in cancer biology. More surprisingly, accumulating data indicates that the HIF1- and/or HIF2-mediated hypoxia responses can be oncogenic as well as tumor suppressive. While the role of HIF in the hypoxia response is well established, recent data support the concept that HIF is necessary, but not sufficient for the hypoxic response. Other transcription factors that are activated by hypoxia are also required for the HIF-mediated hypoxia response. HIFs, other transcription factors, co-factors and RNA poll II recruited by HIF and other transcription factors form multifactorial enhanceosome complexes on the promoters of HIF target genes to activate hypoxia inducible genes. Importantly, HIF1 or HIF2 requires distinct partners in activating HIF1 or HIF2 target genes. Because HIF enhanceosome formation is required for the gene activation and distinct functions of HIF1 and HIF2 in tumor biology, disruption of the HIF1 or HIF2 specific enhanceosome complex may prove to be a beneficial strategy in tumor treatment in which tumor growth is specifically dependent upon HIF1 or HIF2 activity.

Egr-1 is a critical regulator of EGF-receptor-mediated expansion of subventricular zone neural stem cells and progenitors during recovery from hypoxia-hypoglycemia

We recently established that the EGF-R (epidermal growth factor receptor) (EGF-R) is an essential regulator of the reactive expansion of SVZ (subventricular zone) NPs (neural precursors) that occurs during recovery from hypoxic-ischemic brain injury. The purpose of the current studies was to identify the conditions and the transcription factor (s) responsible for inducing the EGF-R. Here, we show that the increase in EGF-R expression and the more rapid division of the NPs can be recapitulated in in vitro by exposing SVZ NPs to hypoxia and hypoglycemia simultaneously, but not separately. The EGF-R promoter has binding sites for multiple transcription factors that includes the zinc finger transcription factor, Egr-1. We show that Egr-1 expression increases in NPs, but not astrocytes, following hypoxia and hypoglycemia where it accumulates in the nucleus. To determine whether Egr-1 is necessary for EGF-R expression, we used SiRNAs (small interfering RNA) specific for Egr-1 to decrease Egr-1 expression. Knocking-down Egr-1 decreased basal levels of EGF-R and it abolished the stress-induced increase in EGF-R expression. By contrast, HIF-1 accumulation did not contribute to EGF-R expression and FGF-2 only modestly induced EGF-R. These studies establish a new role for Egr-1 in regulating the expression of the mitogenic EGF-R. They also provide new information into mechanisms that promote NP expansion and provide insights into strategies for amplifying the numbers of stem cells for CNS (central nervous system) regeneration.

PKCβ promotes vascular inflammation and acceleration of atherosclerosis in diabetic ApoE null mice

OBJECTIVE

Subjects with diabetes mellitus are at high risk for developing atherosclerosis through a variety of mechanisms. Because the metabolism of glucose results in production of activators of protein kinase C (PKC)β, it was logical to investigate the role of PKCβ in modulation of atherosclerosis in diabetes mellitus.

APPROACH AND RESULTS

ApoE(-/-) and PKCβ(-/-)/ApoE(-/-) mice were rendered diabetic with streptozotocin. Quantification of atherosclerosis, gene expression profiling, or analysis of signaling molecules was performed on aortic sinus or aortas from diabetic mice. Diabetes mellitus-accelerated atherosclerosis increased the level of phosphorylated extracellular signal-regulated kinase 1/2 and Jun-N-terminus kinase mitogen-activated protein kinases and augmented vascular expression of inflammatory mediators, as well as increased monocyte/macrophage infiltration and CD11c(+) cells accumulation in diabetic ApoE(-/-) mice, processes that were diminished in diabetic PKCβ(-/-)/ApoE(-/-) mice. In addition, pharmacological inhibition of PKCβ reduced atherosclerotic lesion size in diabetic ApoE(-/-) mice. In vitro, the inhibitors of PKCβ and extracellular signal-regulated kinase 1/2, as well as small interfering RNA to Egr-1, significantly decreased high-glucose-induced expression of CD11c (integrin, alpha X 9 complement component 3 receptor 4 subunit]), chemokine (C-C motif) ligand 2, and interleukin-1β in U937 macrophages.

CONCLUSIONS

These data link enhanced activation of PKCβ to accelerated diabetic atherosclerosis via a mechanism that includes modulation of gene transcription and signal transduction in the vascular wall, processes that contribute to acceleration of vascular inflammation and atherosclerosis in diabetes mellitus. Our results uncover a novel role for PKCβ in modulating CD11c expression and inflammatory response of macrophages in the development of diabetic atherosclerosis. These findings support PKCβ activation as a potential therapeutic target for prevention and treatment of diabetic atherosclerosis.

Apoptosis induction of human bladder cancer cells by sanguinarine through reactive oxygen species-mediated up-regulation of early growth response gene-1

Although the effects of sanguinarine, a benzophenanthridine alkaloid, on the inhibition of some kinds of cancer cell growth have been established, the underlying mechanisms are not completely understood. This study investigated possible mechanisms by which sanguinarine exerts its anticancer action in cultured human bladder cancer cell lines (T24, EJ, and 5637). Sanguinarine treatment resulted in concentration-response growth inhibition of the bladder cancer cells by inducing apoptosis. Sanguinarine-induced apoptosis was correlated with the up-regulation of Bax, the down-regulation of Bid and XIAP, the activation of caspases (-3, -8, and -9), and the generation of increased reactive oxygen species (ROS). The ROS scavenger N-acetyl cysteine (NAC) completely reversed the sanguinarine-triggered apoptotic events. In addition, sanguinarine effectively increased the activation of the c-Jun N-terminal kinase (JNK) and the expression of the early growth response gene-1 (Egr-1), which was recovered by pretreatment with NAC. Furthermore, knockdown of Egr-1 expression by small interfering RNA attenuated sanguinarine-induced apoptosis, but not the JNK inhibitor, indicating that the interception of ROS generation blocked the sanguinarine-induced apoptotic effects via deregulation of the expression of Egr-1 proteins. Taken together, the data provide evidence that sanguinarine is a potent anticancer agent, which inhibits the growth of bladder cancer cells and induces their apoptosis through the generation of free radicals.

Sanguinarine induces apoptosis in human colorectal cancer HCT-116 cells through ROS-mediated Egr-1 activation and mitochondrial dysfunction

We examined the effects of sanguinarine, a benzophenanthridine alkaloid, on reactive oxygen species (ROS) production and the association of these effects with apoptotic cell death in a human colorectal cancer HCT-116 cell line. Sanguinarine generated ROS, which was followed by a decrease in the mitochondrial membrane potential (MMP), the activation of caspase-9 and -3, and the down-regulation of anti-apoptotic proteins, such as Bcl2, XIAP and cIAP-1. Sanguinarine also promoted the activation of caspase-8 and truncation of Bid (tBid). However, the quenching of ROS generation by N-acetyl-l-cysteine, a scavenger of ROS, reversed the sanguinarine-induced apoptosis effects via inhibition of the MMP collapse, tBid expression, and activation of caspases. Sanguinarine also markedly induced the expression of the early growth response gene-1 (Egr-1) during the early period, after which expression level was decreased. In addition, HCT-116 cells transfected with Egr-1 siRNA displayed significant blockage of sanguinarine-induced apoptotic activity in a ROS-dependent manner. These observations clearly indicate that ROS, which are key mediators of Egr-1 activation and MMP collapse, are involved in the early molecular events in the sanguinarine-induced apoptotic pathway acting in HCT-116 cells.

Ubc9 acetylation modulates distinct SUMO target modification and hypoxia response

While numerous small ubiquitin-like modifier (SUMO) conjugated substrates have been identified, very little is known about the cellular signalling mechanisms that differentially regulate substrate sumoylation. Here, we show that acetylation of SUMO E2 conjugase Ubc9 selectively downregulates the sumoylation of substrates with negatively charged amino acid-dependent sumoylation motif (NDSM) consisting of clustered acidic residues located downstream from the core ψ-K-X-E/D consensus motif, such as CBP and Elk-1, but not substrates with core ψ-K-X-E/D motif alone or SUMO-interacting motif. Ubc9 is acetylated at residue K65 and K65 acetylation attenuates Ubc9 binding to NDSM substrates, causing a reduction in NDSM substrate sumoylation. Furthermore, Ubc9 K65 acetylation can be downregulated by hypoxia via SIRT1, and is correlated with hypoxia-elicited modulation of sumoylation and target gene expression of CBP and Elk-1 and cell survival. Our data suggest that Ubc9 acetylation/deacetylation serves as a dynamic switch for NDSM substrate sumoylation and we report a previously undescribed SIRT1/Ubc9 regulatory axis in the modulation of protein sumoylation and the hypoxia response.

Early growth response genes signaling supports strong paracrine capability of mesenchymal stem cells

MSCs provide a promising method for cell therapy through their wound healing and tissue regenerative properties. Originally, MSCs' role in wound healing was thought to be tied to their multipotency, but it is now accepted that MSCs mediate the healing process through their strong paracrine capability. EGF was shown to facilitate in vitro expansion of MSCs without altering multipotency. Our previous data suggest that the molecular machinery underlying MSCs' strong paracrine capability lies downstream of EGFR signaling, and we focus on transcription factors EGR1 and EGR2. Evidence suggests that EGR1 regulates angiogenic and fibrogenic factor production in MSCs, and an EGFR-EGR1-EGFR ligands autocrine loop is one of the underlying mechanisms supporting their strong paracrine machinery through EGR1. EGR2 appears to regulate the expression of immunomodulatory molecules. Chronic nonhealing wounds are ischemic, inflammatory, and often fibrotic, and the hypoxic micro-environment of these wounds may compromise MSCs' wound healing properties in vivo by upregulating the EGR1's fibrogenic effects and downregulating the EGR2's immuno-modulatory effects. Thus, these transcription factors can be potential targets in the optimization of cell-based therapies. Further study in vitro is required to understand MSCs' paracrine machinery and to optimize it as a tool for effective cell-based therapies.

In Vivo and In Vitro Silica Induces Nuclear Factor Egr-1 Activation Mediated by ERK 1/2 in RAW264.7 Cell Line

The transcription factor early growth response gene (Egr-1) is a stress response gene activated by various forms of stress. The effect of silica on transcription and expression of Egr-1 was investigated in rat lung and in RAW264.7 cells. Silica induced the expression of Egr-1 in vivo and was mainly located in alveolar macrophage cells and lung epithelial cells. Furthermore, silica induced Egr-1 mRNA and protein expression in cultured RAW264.7 cells. Immunofluorescence microscopy revealed translocation of Egr-1 to the nucleus in response to silica. The contribution of the extracellular signal-regulated kinase (ERK) pathway to the activation of Egr-1 in response to silica was examined. Exposure to silica resulted in a rapid phosphorylation of ERK 1/2 kinases in RAW264.7 cells. MAP Kinase Kinase (MEK) inhibitor U0126 prevented Egr-1 induction by silica. The results suggest that silica could induce Egr-1 activation in macrophages in vivo and in vitro and that phosphorylated ERK 1/2 may be involved in this action.

Experimental Validation of Methods for Prophylaxis against Deep Venous Thrombosis: A Review and Proposal

The experimental procedure by which the valve cusp hypoxia (VCH) hypothesis of the etiology of deep venous thrombosis (DVT) was confirmed lends itself to testing of methods of prophylaxis. Similar animal experiments could end the present exclusive reliance on statistical analysis of data from large patient cohorts to evaluate prophylactic regimes. The reduction of need for such (usually retrospective) analyses could enable rationally-based clinical trials of prophylactic methods to be conducted more rapidly, and the success of such trials would lead to decreased incidences of DVT-related mortality and morbidity. This paper reviews the VCH hypothesis ("VCH thesis", following its corroboration) and its implications for understanding DVT and its sequelae, and outlines the experimental protocol for testing prophylactic methods. The advantages and limitations of the protocol are briefly discussed.

Combination effects of cigarette smoke extract and ambient ultrafine particles on endothelial cells

Previous studies have shown that ambient ultrafine particles with diameters less than 100nm (UFPs) can pass from the lungs to the circulation because of their very small diameter, and induce lung oxidative stress with a resultant dysfunction of lung endothelial cells. However, no studies have addressed the potential combined effects of UFPs and cigarette smoke on vascular endothelial cells. We hypothesized that co-exposure to UFPs and cigarette smoke extract (CSE) may cause combined effects on activation of endothelial cells and dysfunction of endothelium by oxidative stress through activation of NADPH oxidase. We determined the effects of UFPs with or without CSE on mouse pulmonary microvascular endothelial cells (MPMVEC) obtained from C57BL/6J (wild-type) and gp91(phox) knock-out mice (gp91(phox) is one of the key components of NADPH oxidase, one of ROS generators). Our results showed that exposure of MPMVEC from wild-type mice to UFPs or CSE, at a non-toxic dose, induced reactive oxygen species (ROS) generation, increased phosphorylation of p38 and Erk1/2, and up-regulated early growth response -1 (Egr-1) and IL-6 genes. These effects were significantly enhanced when cells were co-exposed to both UFPs and CSE. However, exposure of MPMVEC from gp91(phox) knock-out mice did not induce the above effects. Furthermore, UFPs- and/or CSE-induced Egr-1 mRNA upregulation was attenuated significantly when cells were pre-treated with p38 specific inhibitor, SB 203580, or MEK1/2 inhibitor, PD98059, and Egr-1 siRNA treatment abolished UFPs- and/or CSE-induced overexpression of IL-6. Our results suggest that UFPs and/or CSE caused activation of NADPH oxidase, resulting in ROS generation that led to activation of MAPKs through induced phosphorylation of p38 and ERK1/2 MAPKs and upregulation of Egr-1. Those effects may further result in endothelial dysfunction through production of cytokines such as IL-6. Our results suggest that co-exposure to UFPs and CSE causes enhanced injury to endothelial cells.

GPER mediates the Egr-1 expression induced by 17β-estradiol and 4-hydroxitamoxifen in breast and endometrial cancer cells

Early growth response-1 (Egr-1) is an immediate early gene involved in relevant biological events including the proliferation of diverse types of cell tumors. In a microarray analysis performed in breast cancer cells, 17β-estradiol (E2) and the estrogen receptor antagonist 4-hydroxitamoxifen (OHT) up-regulated Egr-1 through the G protein-coupled receptor named GPR30/GPER. Hence, in this study, we aimed to provide evidence regarding the ability of E2, OHT and the selective GPER ligand G-1 to regulate Egr-1 expression and function through the GPER/EGFR/ERK transduction pathway in both Ishikawa (endometrial) and SkBr3 (breast) cancer cells. Interestingly, we demonstrate that Egr-1 is involved in the transcription of genes regulating cell proliferation like CTGF and cyclin D1 and required for the proliferative effects induced by E2, OHT, and G-1 in both Ishikawa and SkBr3 cells. In addition, we show that GPER mediates the expression of Egr-1 also in carcinoma-associated fibroblasts (CAFs). Our data suggest that Egr-1 may represent an important mediator of the biological effects induced by E2 and OHT through GPER/EGFR/ERK signaling in breast and endometrial cancer cells. The results obtained in CAFs provide further evidence regarding the potential role exerted by the GPER-dependent Egr-1 up-regulation in tumor development and progression. Therefore, Egr-1 may be included among the bio-markers of estrogen and antiestrogen actions and may be considered as a further therapeutic target in both breast and endometrial tumors.

Xanthine oxidase-derived ROS upregulate Egr-1 via ERK1/2 in PA smooth muscle cells; model to test impact of extracellular ROS in chronic hypoxia

Exposure of newborn calves to chronic hypoxia causes pulmonary artery (PA) hypertension and remodeling. Previous studies showed that the redox-sensitive transcription factor, early growth response-1 (Egr-1), is upregulated in the PA of chronically hypoxic calves and regulates cell proliferation. Furthermore, we established in mice a correlation between hypoxic induction of Egr-1 and reduced activity of extracellular superoxide dismutase (EC-SOD), an antioxidant that scavenges extracellular superoxide. We now hypothesize that loss of EC-SOD in chronically hypoxic calves leads to extracellular superoxide-mediated upregulation of Egr-1. To validate our hypothesis and identify the signaling pathways involved, we utilized PA tissue from normoxic and chronically hypoxic calves and cultured calf and human PA smooth muscle cells (PASMC). Total SOD activity was low in the PA tissue, and only the extracellular SOD component decreased with hypoxia. PA tissue of hypoxic calves showed increased oxidative stress and increased Egr-1 mRNA. To mimic the in vivo hypoxia-induced extracellular oxidant imbalance, cultured calf PASMC were treated with xanthine oxidase (XO), which generates extracellular superoxide and hydrogen peroxide. We found that 1) XO increased Egr-1 mRNA and protein, 2) XO induced the phosphorylation of ERK1/2 and, 3) pretreatment with an ERK1/2 inhibitor prevented induction of Egr-1 by XO. siRNA knock-down of EC-SOD in human PASMC also upregulated Egr-1 mRNA and protein, activated ERK1/2, and enhanced SMC proliferation and reduced apoptosis. We conclude that an oxidant/antioxidant imbalance arising from loss of EC-SOD in the PA with chronic hypoxia induces Egr-1 via activation of ERK1/2 and contributes to pulmonary vascular remodeling.

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.

GGPPS, a new EGR-1 target gene, reactivates ERK 1/2 signaling through increasing Ras prenylation

Cigarette smoke activates the extracellular signal-regulated kinase (ERK) 1/2 mitogen activated-protein kinase pathway, which, in turn, is responsible for early growth response gene-1 (EGR-1) activation. Here we provide evidence that EGR-1 activation can also reactivate ERK 1/2 mitogen activated-protein kinase through a positive feedback loop through its target gene (geranylgeranyl diphosphate synthase) GGPPS. For the first time, the GGPPS gene is identified as a target of EGR-1, as EGR-1 can directly bind to the predicted consensus-binding site in the GGPPS promoter and regulate its transcription. Long-term observations show that there are two ERK 1/2 phosphorylation peaks after cigarette smoke extract stimulation in human lung epithelial Beas-2B cells. The first peak (at 10 minutes) is responsible for EGR-1 accumulation, and the second (at 4 hours) is diminished after the disruption of EGR-1 transcriptional activity. EGR-1 overexpression enhances Ras prenylation and membrane association in a GGPPS-dependent manner, and it augments ERK 1/2 activation. Likewise, a great reduction of the second peak of ERK 1/2 phosphorylation is observed during long-term cigarette smoke extract stimulation in cells where GGPPS is disrupted. Thus, we have uncovered an intricate positive feedback loop in which ERK 1/2-activated EGR-1 promotes ERK 1/2 reactivation through promoting GGPPS transcription, which might affect cigarette smoke-related lung pathological processes.

A concerted HIF-1α/MT1-MMP signalling axis regulates the expression of the 3BP2 adaptor protein in hypoxic mesenchymal stromal cells

Increased plasticity, migratory and immunosuppressive abilities characterize mesenchymal stromal cells (MSC) which enable them to be active participants in the development of hypoxic solid tumours. Our understanding of the oncogenic adaptation of MSC to hypoxia however lacks the identification and characterization of specific biomarkers. In this study, we assessed the hypoxic regulation of 3BP2/SH3BP2 (Abl SH3-binding protein 2), an immune response adaptor/scaffold protein which regulates leukocyte differentiation and motility. Gene silencing of 3BP2 abrogated MSC migration in response to hypoxic cues and generation of MSC stably expressing the transcription factor hypoxia inducible factor 1alpha (HIF-1α) resulted in increased endogenous 3BP2 expression as well as cell migration. Analysis of the 3BP2 promoter sequence revealed only one potential HIF-1α binding site within the human but none in the murine sequence. An alternate early signalling cascade that regulated 3BP2 expression was found to involve membrane type-1 matrix metalloproteinase (MT1-MMP) transcriptional regulation which gene silencing abrogated 3BP2 expression in response to hypoxia. Collectively, we provide evidence for a concerted HIF-1α/MT1-MMP signalling axis that explains the induction of adaptor protein 3BP2 and which may link protein binding partners together and stimulate oncogenic MSC migration. These mechanistic observations support the potential for malignant transformation of MSC within hypoxic tumour stroma and may contribute to evasion of the immune system by a tumour.

Evaluation of 309 environmental chemicals using a mouse embryonic stem cell adherent cell differentiation and cytotoxicity assay

The vast landscape of environmental chemicals has motivated the need for alternative methods to traditional whole-animal bioassays in toxicity testing. Embryonic stem (ES) cells provide an in vitro model of embryonic development and an alternative method for assessing developmental toxicity. Here, we evaluated 309 environmental chemicals, mostly food-use pesticides, from the ToxCast™ chemical library using a mouse ES cell platform. ES cells were cultured in the absence of pluripotency factors to promote spontaneous differentiation and in the presence of DMSO-solubilized chemicals at different concentrations to test the effects of exposure on differentiation and cytotoxicity. Cardiomyocyte differentiation (α,β myosin heavy chain; MYH6/MYH7) and cytotoxicity (DRAQ5™/Sapphire700™) were measured by In-Cell Western™ analysis. Half-maximal activity concentration (AC₅₀) values for differentiation and cytotoxicity endpoints were determined, with 18% of the chemical library showing significant activity on either endpoint. Mining these effects against the ToxCast Phase I assays (∼500) revealed significant associations for a subset of chemicals (26) that perturbed transcription-based activities and impaired ES cell differentiation. Increased transcriptional activity of several critical developmental genes including BMPR2, PAX6 and OCT1 were strongly associated with decreased ES cell differentiation. Multiple genes involved in reactive oxygen species signaling pathways (NRF2, ABCG2, GSTA2, HIF1A) were strongly associated with decreased ES cell differentiation as well. A multivariate model built from these data revealed alterations in ABCG2 transporter was a strong predictor of impaired ES cell differentiation. Taken together, these results provide an initial characterization of metabolic and regulatory pathways by which some environmental chemicals may act to disrupt ES cell growth and differentiation.